Anatomy stems from the origins in greek meaning “Ana” or up, and “tomia” cutting, latin anatomnia, and french “anatomie”. Sometimes people refer to it’s greek origin as meaning “dissection”.

Anatomy is the study of the structure of the body and the relationship, or organisation between those organs and system. Physiology deals with the function of those structures. Physiology is considered a sub discipline of biology. Physiology focuses on how the organs, systems, cells and biomolecules carry out the physical and physical functions in a living system.

There is pphysiology based on the organism or taxa like animal physiology, plant physiology which is considered botany, microbial physiology, viral physiology, insect phyiology

Then there is phsyiology based on the level of organisation: cell physiology, molecular phsyiology, system physioloy, organismal phsyoilogy, ecological phsyiology, integrative phsyiology.

common elemtns of life like death, sex, eating sleeping, and thinking are things we study through anatomy and physiology.

Cadaviers or dead bodies are often used to study anatomy. Complementarity oroder ?, or the hierarchy of roganisation of the body is the following:

  1. chemical
  2. Cellular
  3. tissues
  4. organs
  5. organ systems
  6. the ody

Above the level of chemicals is the cells, one of the most comon being red blood cells.

Cells geoup together to organise into the next level that is tissues.

When two or more tissue types ombine they form orand.

when organs work togther they form systems.

All the organ systems combine to form the human body. The body is trying to maintain steady internal conditions, in spite of what may be going on external to the body. This is called homeostasis.

An example being if the temperature is hot outside the body will work to keep it cool.


The classic anatomical position is the body standing erect, faciing straight ahead.

The front of the body is called anterior or ventral.

The back part of the body is considered posterior, or dorsal.

Something that is above something else or towards the top of the body is called superior, or cranial on the body.

Inferior, or caudial means more towards the bottom of the body.

The area closer to the midline of the body is called medial, and as it gets further away lateral.

Proximial is as you get closer to the trunk, and sital is as you get further away from the trunk.


Saggital plane, or mediun plant is cutting the body down the middle from left to right. A plane parrellel tothe saggital plane is the para saggital plane.

The coronal, or frontal plane is cutting the body vertically from front to back, like slicing left to right through the midline of the body at the side, and vice versa.

The transverse, or horizontal plane divides the body into top and bottom.

THe head neck, body and tordo are considered the axial part of the body. THe apppendicular, or the appendige parts of the body are the arms and legs.


Amoeba’s are single cells, where a shumans are trillions of cells working together through processes to achieve an outcome. Thus, cells specialise in something, this is called cell specialisation. Cells are the most basic building blocks in the human body. When groups come together to form a common function we call that tissues. The word tissue mean s”woven”? The study of tissues is called histology. The word origin is the Greek word “histos” meaning tissue, and “logia” meaning science.

We needed microscopes to study the bodies tissues. Given microscopes weren’t invented until 1590 it makes it a reasonably young science.

Anton Van Leewenhook ? took mirscopes from 50 x magnification to 270 x ? He was the first to see bacteria, and muscle fibres which was why people refer to him as the father of microbiolgoy.

Later hwen we invented stains and yes it was easier to see more due to more ocntrast. ONe of the earliest dyes was “carmine” which came from crushed up ?cochineal ? insetcts. The word origin of carmine is “carmin”in french, o r “irmiz” in Arabic.

We soon learned that a powerful microscope with a compatible stain could open up knowledge in wonders of the micro world, including human tissues, and how they come together to function for living organisms.

Two or more types of tissue when working together is called an organ.

There are four primary tissue types:

nervous tissue – communicates and conrolt the body

The central and perihperal nervous sytem combine to regulate all the body functions. ? Neurons nad glial cells are the two primary types of cells i nthe nervous system. ? The neuron is made up of the cell body, also called soma ?, the denedrite which look like proturding trees , and the axons which look like long connecting legs ?. The axon is like the transmission cable.

The brain is an example of something that is mostly nervous tissues ?

The other type of cells are called glial cells.

muyscles tissues – allow the body to move

Muscles tissue can contract and are well vascularised, meaning they get good blood flow.

There are three types of muscles cells:

smooth muscle tissue – This lines the wall of your blood vessels, and most of your organs. This muscle contracts slowly and automatically, and has no stripes going across it. If you remember the muscle is smooth, and contains no striations it helps.

cardiac muscle tissue – Contrary to muscle tissue this works involuntary. The contractoin of this tissue allows blood to move through the circulatory systedm. The muscle is striped, referred to as “striations” or “striated”. This muscle has cirular light bands going around it ? The connection of cells have a branching structure ?

skeletal muscle tissue – The skeletal muscle tissue is the one that pulls on your bone to allow you to move, and works largely voluntarily. Intercalated discs link the cells together, and define their borders. This is long and straight cells with multiple nuclei, and striations, or stripes that goes around it.
The shape of each cell is related to it’s function.

epithelial tissues – The proper epithelium covers and protects the outside and inside body. The glandular epithelium forms glands and secretes hormones, and other substances. The epithelium in parts of the body is invaginated, or turned inside out, or in on itself, folded back in to form a cavity or pouch.

They don’t have a direct blood supply ?, instead they rely on the supply of blood in the supporting connective tissues.

There are three basic shapes to epithelial cells: 1. Squamous 2. Cuboidal 3. Columnar

  1. Squamous cells are flatish cells, that quickly absorb and diffuse substances almost like a thin membrane ? The nucleus of the cell is also flat. Squamous cells are fairly flat which makes it easy for materials like oxygen to cross to the other side. Where abroption or transportation is important such as in the air sacs of the lungs you will see these cells ?

Cells create time and energy in the body to make, so in places like the mouth and skin where we need a more readily supply of new cells than other cells the body will tend to use squamous ?

  1. The cuboidal cells are shaped like a cube, are similiar size in height and width. They absorb nutrients and produce secretions. Their mucleus is more ciruclar than squamous cells.
  2. Columnar cells are long and thick, and cuhsion under lying tissues. Thei nuclei looks eliptical, alsmost as if it’s been stretched.

Cells like the stomach lining are normally columnar or cuboidal because they need room to make secretions, and other substances.

We can then classify epithelium by layers. A simple epithelium can have one layer. Multiple layers of epithelium is called stratified. They’re stacked vertically much like laying bricks on top of each other.

Pseudo stratified is basically one layer ?, but the cells can be different shapes and sizes.

If a tissue is referred to by two names, usually the first name refers to the number of layers, and the second name the shapes of it’s cells.

The epithelial tissue is also named by the direction the cells face. The apical side ?, or upper side points towards the outside of the body, whether it is towards the outside of the body or lining an internal cavity. ?body. epitheilial cells are polar ?

The basal side, is the internal side or surface.

These cells are selectively permeable allowing for some level of absorption, filtration and excretion of substances.

There is also glandular epithelium which forms the endocrine glands. The endocrine glands secrete hormones. The exocrine glands secrete their juices into tubes or ducts, as opposed to direct into the blood like the endocrine glands. ? The thyroid as an example is an endocrine gland. Examples of exocrine gland secretions are sweat, or mother’s milk if you’re lactating.

connective tissues – prdoid euspport of the bpodies. This is the most abundant tissue. It holds us together. It helps us move, transport substances in the body, store flu9id reserve and energy, insulate, protect and supoprt us.

There’s four types of connective tissue:

  1. Proper connective tissue – This is the type found in your skin. Fat is a type of proper connective tissue that provides insulation, ad nd fuel storage.
  2. Bone connective tissue –
  3. Cartlidge connective tissue –
  4. Blood connective tissue –

The bones, tendons, and ligaments support and portect and organs, and give us the skeleton which allows us to move. COnnective tissue all develop from mesenchyme.

Connective tissue has varied levels of vacularity, or blood flow. As an example cartlidge has no blood vessels. Most connective tissue is composed os the extra cellular matrix. The extra cellular matrix has sometimes been referred to as the ” filler” substance existing cells in an organism. is mainly made of two components, ine is called the groound substance. The ground substance is a felxible material ? mostly non living ? that fills in the spaces in between cells, and protects the cells.

Some connective tissue can be hard to chew for humans when eating animals which is partly why we began cooking animal meat. It wasn’t until the advent of cooking that we were able to de nature the animal extra cellular matrix ? is full of fibres, not cells. As an example some animal skin is held on with strong fibres. Cooking it allows the skin to seperate more easily from the rest of the flesh.

The connective tissue can be divided into loose and proper.

The loose connective tissue can be areolar, reticular and adipose.

The dense connective tissue can be regular, ireegular, and elastic.

Loose connective tissue is more common than dense connective tissue in humans.

Examples of loose connective tissue includes fibroblast cells, collagen fibres, and elastic fibres ?

Areolar tissue ?.

Adipose tissues include adipocytes, nucleus, and lipid vacuole.

Some tissues have more give such as , where as dense connective tissues such as tendons have less give.


Another type of tissue is cartlage. Catilage doesn’t have any blood or nerves. There’s three types of cartilage: hyaline, elastic and fibre. Hyaline is the most common type of cartilage. It contains chondrocytes and lacunae? Hyaline cartiladge looks glassy under a microscope hence hyal

Elastic cartilage is similiar to hyaline but with more elastic fibres, but in places where more elasticness or stretchiness is needed.

Fibro cartilage has many thick layers of collagen. Chondrocyte, and collagen fibres.

Bone looks like osseous connective tissue ?

There is spongy anf compact bone tissue. Spongy bone tissue is strong and poreous. In the poeous parts it stores bone marrow.

Contary to spongcy, compact bone tissue is more dense with an osteocyte within a lacuna ?

Even the leukocytes, that is the white blood cells are considered connective tissue cells.

Glycosaminlglycans are long, linear polysaccarides consisting of repeating disaccaride uints.

Collagen are strong fibress

Elastic fibre’s are long and thin, which callows them to strecth like rubber bands.

Reticular fibres are shorter collagen fibres with a coating of glycoprotein.

Cells have a mature and immautre phase.

The word “blast” means “forming”. As an example chondroblasts are the blast cells of cartidlge (spongy tissue ?). Osteoblasts. are the blast cells of bone. Once the blasts reach a mature ? phase the blast, changes it’s suffix to “-cyte”.

Proteoglycans ar ethe primary substance in the extra ceulla matrix.

The red blood cells are called erythrocytes. Proteins dissolved in the plasma form fibre like structures. White blood cells are called leukocytes


The skin, hair, nails, sudoriferous (sweat) and sebaceous (oil) glands from your integumentary system. You’ve got three million sweat glands. The skin has three layers. The epidermis is the layer you can see.
The skin is a protectant to the outside world, it transmits sensatio to the nrevous sytem, regulates temperatures, is responsible for vitamin d absorption / synthesis ?, it’s functio nis exretory. Small amounts of contents of the urine such as urea may be disposed of in sweat.urea. We sweat to regulaet body temperature. This is called insensible perspiration ? we usually don’t nitce it.

On a hot day we notice it more, is called sensible perspiration. When the need blood in the core organs the blood vessels in the skin tend ot restrict sending blood back into the core.

Skin may change colour indiactive of different underlying issues. When we have cardiovasulcar challenges that are preventing the skin from getting the circulation it needs we see the skin turn a shade of blue. This is called cyanosis. Blood that is low in oxygen can look blue.

When the skin is a yellow colour we call this jaundice. This may be indiciative of something liver related.

It provides a protection to the body, a barrier to pathogens, and regulates the amount of water released from the body into the atmosphere. It is made of stratified squamous tissues, that is flat cells, with a flattened looking nucleus that is stacked one on top of each other like bricks ?.

The skin is loaded with cutaneous sensory receptors. They’re somtimes called corpuscles. The skin can register touch, pressure, temperature, pai and other sensation. When the skin is red it’s called erythema it can be indiactive of fever, inflammatio nor allergy. Discolouration may be easier to see around the bed (synonyms) of fingers and toses, or blood vessels under the skin.

There is tactile corpuslces that sense touc h?, lamellar corpuscles register touch.

Epidermis comes from the Greek word “epi” meaning ” over” or ” upon” and ” derma” meaning skin. Your epidermis is goes through a complete cell cycle every 4 – 6 weeks. THe epidermis has 4-5 layers and is avascular, so it’s reliant on oxygen and nutrients from the layer below.

The keratinocytes are the building blocks of keratin, which is a tough protein.

The dermis which is below the epidermis, and they hypodermis is below that. The dermis is where most of the activity is done in the skin ?, the blood is cirulcated, where we feel. In between the epidermis and dermis is the merkel cells which is the snesory recption for touch.

The dermis is where tattoo ink is inserted when tattooing below the epidermis.

The hpodermis at the bottom is composed mostly of adipose, which is fatty tissue. ?

The building blocks of keratin, which is a tough fibre is keratinocytes.

The skin protects youur body against pathogens as best it can, helps you to withstand tempature, and systheises the hormone

The melanocyte is the cell that synthesises melanin. ? vitamin d also called calcitriol is made in the kidney ? Melanian is responsible for giving the skin it’s colour. It’s called a pigment. The colour of the skin is not dictated by the number of melanocytes. The breadth of the cellular extension affects the amount of melanin that they contain. ?
Langerhan cells
THe skin is our proectant from the outside world so we have a lot of immune cells in them. Langerhan cells, look star shaped, a

The stronger skin such as that on the palms of your hands, and soles of your feet is called ‘thick skin’, which has five layers, where as the thin skin has four layers.

The layers of the skin include:

stratum corneum – This is the most outermost layer, and the roughest with 20-30 layers of dead cells.
stratum lucidem
stratum granulosum

The layers of the epidemris include:

stratum spinosum
stratum basale

The papillary layer is areolar connective tissue, dermal papillae, sometimes called “dermal ridges” or “friction ridges”. Friction ridges are commonly associated with finger prints.

The sweat glands have two types eccrine glands which there are more of. They’re in the palms, fet, and forehead. The second type is called apocrine glands that empty into the hair follicles near where the linbs meet the trunk, the under arms and groin.

It’s the bacteria that tend to create the smell when we sweat which is why some deoderant is designed to protect from us

The ceruminous glands make the ear wax, cerumen. The mammary glands secrete milk.

A tendon is an example of “dense connective tissue” with a lot mor c ollagen

There is loose connective tissue: areolar, adipose, recticular

Adipose tissue is the fat tissue. It is mainly adipocytes, nucleus and lipid vacuole. Adipose is on average 18% of our body weight.

The recticular tissue holds the blood in place in many of the organs ?

Fibroblast cells, elastic fibers, collagen fibers.

Recticular layer, dense irregular connective tissue


The nail has the body, root, and bed. nail


The nervous system has been likened to the electrical cords of the body. YOu can think of the nervcous system as being comprised of: sensory input, integration, and motor output.

It is dviided into the CNS, central nervous system, and perihperial nervous system, PNS.
When a neuron is stimulated ? it fires an electrical signal that fires down it’s axon to other neurons. It is one signal, strength and speed. The frequency or speed can be better.

The nerve impulse is called the action potential ? . Voltage which is sometimes called electromotive foce, EMF, electric pressure, or electric tension. Voltage can cause currents to move ? Moving charges are called a current, basically that is the flow of electrictry from one point to another. Voltage is the electric potential difference betwen two places. There are two types of voltage: AC and DC.

The resting membrane potential is -70mW The axon? of the neuron has a naegative charge, while outside of that has a positive charge. Outside of a neuron there is sodium ions with a positive charge. Inside the cells there are potassium ions with a positive charge.

Inside the cell there are potassium ions which have a positive charge, but there is also bigger negatively charged proteins. Because there are more sodium ions outisde, than potassium ions sinde the cell has an overall negative charge.

For every two potassium ions it pumps into the cell, it pumps out three sodium ions. The difference is called an electrochemical gradient. The channels that these ions use to go in and outside the cell is called voltage gated channels.

There’s also ligand gated channels that only allow certain neuro transmitters in. There’s also mechanically gated channels. The electrical evebts in neurons is based on the movements of ions.

A small change in gradeitn energy is called a graded potential? The strength in the action potential is the same, what changes is the frequency. The speed is affected by whether there is a myelin sheath on the axon. Myelin sheets are formed by schwann cells wrapping themself around the axon in the PNS. Axon with a large rdiameter conduct more quickly as they offer less resistance.

As the cells don’t touch each other there are spaces in between the myelin called the ” nodes of ranvier”

In the CNS the mylineeation occurs by the ogliodendrocytes wrapping around the axon. This style of communication comes from the Latwin word for leaping called ” saltatory conduction”.

When there is a difference in charge between cells, we call this the “membrane potential”.

The action potential goes through the stages of resting state, depolarisation, repolarisation, and hyperpolarisation.

The neurons cell body, the dendrities extending out look like treee branches. The axon is like the communicator?

A process, or a part that projects out. Tjhe vast majrotiy of neurons are multipolar neurons. They have a cell body, dendrite and axon, but has multiple densrties ? A bipolar neuron has a sole axon, and only one dendrite. Axons are essentially the transmission lines of thenervous system, as bundles they make nerves. The longest axons in the body are those of the sciatic nerve ? that run from the spine to the foot.

In vertabrates the axons sheathed in myelin which is one of two types of glial cells. The peripheral nuerons are called Schwann cells, and the CNS are called oligodendrocytes.

There are unipolar neuronds ? that are found mainly in the sensory receptors.

The meeting point between two neurons is called the synapse. The synapse the communication junctions between the neurons allow the neurons to work together. Neurons like people need each other to carry out their biological tasks. Synapse comes from a Greek word that can mean conjunction, or to fasten, or to join. The term was first used by Michael Foster in his ” Textbook of physiology”. The term was suggested by Arthur Woollgar Verral as a term meaning connection between two elements. Foster has apparently originally struggled to reconcile a name for a

The brain has over 100 trillion synapses, up to 1000 trillion synapses by some estimates. There are two types of synapses both chemical and electrical. The chemical is slower, more precise, and more abundant, where as the electrical is more immediate, and me be less precise. The synpases commuhicate through gap junctions.

The chemical signals are called neurotransmitters. Even though the neurons never touch they communicate, there is a tiny gap called a synaptic cleft. These diffuse across the synaptic cleft. When neurons communicate they go from the presynaptic neuron to the presynaptic terminal, called th axon terminal ?

When the action potential travels along the axis of a neuron it reaches the pre synaptic terminal. This has synpatic vesicles which contain thousands of molecules of a neuro transmiters. On the post synaptic membrane of the target cell there are receptors.

There is a voltage gated ion channel called a voltage gated calcium channel. The voltage gated calcium channel play an important role in neuro transmitter release. It activates the calcium channels at the pre synaptic terminal.

In the embryo electrical synapses are more common than chemical ones, but they slowly get replaced through neural development.


Our CNS grows out of a neural tube in the embryo. It expands and forms the spinal cord at one end, and the cranium at the other.
dura matter, arachnoid, and pia matter.

The brain is responible for thinking and remembering, the spinal cord. The brain and spinal cord is protected by bones, and the meninges which is three layers: dura matter, arachnoid, and the pia matter.

In the ventricles, or the spaces in the brain there is something called the choiroid plexuses that produced cerebrospinal fluid (csf). The brain has different areas that are responsible for different functions. Some of these sections work more independaently than others.

The three pieces from front to back are called Forebrain (prosencephalon), midbrain (mesencephalon), and (hindbrain) rhomencephalon. These are called vesicle or chambers.

This then develops into further parts. The prosencephalon divides into the end brain (telencephalon), and the interbrain (diencephalon).

The rhomenceaphlon divides to form the midbrain (mesencephalon), spinal brain (myencephalon).

The afterbrain (metencephalon) does not divide. The brain stem consists of three parts starting with the mid brain. Below the mid brain to pons, and medulla oblongata. The mid brain combines the upper brain functions.

The cerebellum is part of the hind brain in all vertabrates, and is responsible for movement and balance. It seems to contribute especially to the prescise coorindation needed in movement. It’s located in the posteior cranial fossa.

Sitting anteriorly to the cerebellum is the fourth ventricle, pons and medulla. The cerebellum contains more neurons than the neocortex by over three fold. The cerebellum is primarily made up of the cerebellar cortex, which is mainly gray matter ?

Neurons that are grouped, that send signals to organs are known as the motor section of the brain.

The diencephelon consists of the thalamus, hypothalamus, epithalamus, and mammillary body. It also has the limbic system which is considered the centre for emotions. The thalamus is a centre for receiving pain. The thalamus seems to be one of the areas most consistently activated when the human brain receives painful stimuli.

The limbic system, previousl known as the limbic lobe is associated with emotional life, and memory transformation from short term to long temr ?

The brain has been divided into three parts: the reptilian parts of the brain, the limbic system, and the neo cortex. Many parts of the reptilian brain are considered more primitive or insitictual. Things such as eating, drinking, sleeping, mating, and avoiding danger.

The telencephalon becomes the largest area of the brain, that performs what is considered the highest functions. It is called the cerebrum, that is composed of grey and white matter. The grey matter is usually on the outside ?. The white matter on the inside. The ridges are called ” gyrus” singular or”gyri plural. The small grooves on either side of the gyri, are called sulci.

The seperation between the left and right hemisphere is called a “fissure”, more specifically the “longitudinal fissure”. ” Fissure” comes from the latin word fissura, plural fissurae.” These two hemispheres communicate through the “corpus collosum”. The corpus callosum is a bundle of nerve fibres shaped like the English letter “C” that stretches across the midline of the brain ultimately connecting both the left and right hemispheres of the brain.

The front part of the cerebrum is called the frontal or coronal cortex. The human cerebral hemisphere is organised into four lobes: the fromtal, parietal, temporal and occiptal lobes. Some times people divide the brain into five lobes: frontal, parietal, occipital, temporal and insula, the latter sometimes called the Island of Reil.

If we chunk the areas of the brain into four loves only, both sides contain these lobes.

The occipital lobe as the posterior part of the brain is primarily responsible for vision. The frontal lobe is considered the more recently evolved part of the brain. Broca’s area which is linked to being responsible for speech production usually lives in the dominant hemisphere.

The parietal lobe sits in between the frontal lobe, and the occipital lobe. It sits above the temporal love. The pariteal love is related to the sensation of touch, pressure, pain and temperature.

The temporal love is responsible for the auditory area of the brain, including language and speech comprehension. The auditory cortex is located on the upper part of the auditory lobe. ? The temporal lobe contains wernicke’s (pronounced ‘vernicke’s’ area) which is specifically meant to be responible for the comprehension of written and spoken language.

Using Brodmann’s classification, Wernicke’s area is typically thought of as being Brodmann’s area 22. This is located in the superior temporal gyrus in the dominant cerebral hemisphere.

The tempotal love also contains the hippocampus, and the amygdala. In plural it is hippocampi, which we have in each of the two hemispheres of the brain. It is part of the limbic system. It helps play a role in ?

The amygdala is almond shaped, coming from the Latin origin of the same.

The perihperal nervous system has the sensory division, also called the afferent divion which pick up sensory stimuli and transmits these impulses? from the snesory receptors towards the CNS,. Most of these are unipolar.r

There are interneurons that transmist information between the ssnesnory and motor neurons.

and the motor division which is called the efferent division, sends instuctions from the CNS to the rest of the body. These are mostly multipolar.

The motor division of the nervous system, has the somatic, which is also called the voluntary nervous system deicated to things such as the muscular skeltal system ?, and the autonomic nervous system, some times called the involuntary nervous system that keeps your heart, lungs, digestion working.

The autonimic nervous system has the parasympthatheitc, and sympathetic division. The autonomic nervous system components, the paarasympathetic and sympathetic while they serve the same organs ? They sometimes have what appears to have oppositie effects, or antagonistic functions.

The sympathetic nervous system overall has more of a stimulating effect, while the parasympaehtic tends to calm things down.

The parasympathetic nervous system has been referred to as “rest and digest”. It slows the heart rate, increases intestinal activity. It’s been referred to as “feed and breed”.

The parasympaethetic nerves start from the craniosacral area at the base of the brain, and from the sacrum. They got the name “parasympaethtic”

The origins of the nerves in the sympathetic nervous system have been called “thoracolumbar” because they originate in the thoracic area of the body. The Greek origin of the word “para” means ” alongside”, and it was named for this reason.

In the PNS groups of neuron cells bodies are called a ganglion. Think of a ganglion as being a group of nerve cell bodies that’s encapdulated anywehre outside the brain, and spinal cord. The plural form of a ganglion, is ganglions, or ganglia. The word Ganglion was used by Galon for the complex nerve centres.

We have both sympaethetic and parasympethtic ganglia. The sympaethetic ganglia run either side of the spinal cord.

A cluster of neurons found in the CNS is called a nucleus.

sympathetic” means to have a fellow feeling, or be affected by like feeling. Given the size of the nerves coming out of

While it’s easy to see the parasympathetic, and sympathetic functiosn of the autonomic nervous system as being oppositie, they’re often referred to as being complimentary.

The sympathetic nervous system has been referred to as stimulating the bodies “fight, flight or freeze” response. People sometimes think of the sympathetic nervous system as being activated when we are under stress. m

The neurons in the transmission of signals through the sympaethtic nervous system are called pre ganflionic and post ganglionic depending on whether the fibres appear before or after they run into the ganglion. The pre ganglionic fibres are shorter than the post ganglion fibres in the sympathetic nervous system.

In the parasympathetic nervous system the reverse is true, the pre ganglinoistic fibres are long, and the post gnalgionic fibres are short. They eventually reach their effectors which are usually muscles or glands that respond to a stimulus at the terminal end of the nerve fibre.

An example of the path of travel would be a signal transmitted from the preganglionic cell to the ganglion, to the postganglionic cell to the effector organ to create a response.

Norepinephrine or noradrenaline is released from the postganglionic sympathetic nerve terminals. When this same chemical is released from the adrenal glands it’s considered a hormone. When it’s released by neurons in the nervous system it’s called a neuro transmitter.

The neuro transmitters cross the synapse as the signal makes it’s way to the effector site to stimulate a response. Norephrine is what is released in the sympathetic nervous system in the postganglionic fibres.

The adrenal glands can release epinephrine and norepinephrine, or adrenaline, and noradreline as it’s called, into the bloodstream to send a more blanket signal to other organs. As this adrenaline travels through the bloodstream it triggers the speed of the heart beat to increase driving more blood through the body including to the peripherary. The lungs take in more oxygen. This combination of extra oxygen, and increased blood circulation encourages mental alertness.

With norepiniphrine being able to be made in the adrenal glands, and sympathetic neurons it belongs to a group of compounds called ” catecholamines”. When norepineprine is in the sympaethetic nervous system it’s going across the synapse, when it’s in the adrenal glands

Norepinephrine, also called noradrenaline is used to prepare the body for action, or a threatening stimulus. It seems to help alertness, memory and the focusing of attention. Physically it moisten the eyes, dilates the pupils, increases the amount of blood pumped by the heart, can increase body heat,

It can constrict blood veels increasing blood pressure, and speeds up lipolysis, or the conversion of fat into substances that can be used for energy. It also createss a decrease in digestive activity.

The senses including hearing and sound get sharper. After the adrenaline response, the hypothalamus then activates the HPA axis, which is the hypothalamus, pituitary gland, and the adrenal glands. If there is something ongoing that the nervous system percieves as a stress

Aceytl chlone, or ach, is a very common neuro transmitter found in the nervous system.

The action of the sympathetic and parasympathetic nervous system have been linkened to an accelerator, and brake in a car. With the sympathetic nervous system being the gas, or accelerator pedal, and the parasympathetic system being the brake.

When actived the SNS triggers a vasoconstriction of the blood vessels.
Neurons are the most well known, they are surrounded by glial cells.

In the central nervous sytem these glial cells are called astrocytes, microglial, ependymal, and ogliodendrocytes. The glial cells make up roughly half the mass of the brain. ?

microglial cells
Ependymal cells


The peripheral nervous system, contains nerves and ganglia that operate outside of the brain and spinal cord. The central nervous system connects to the peripheral nervous system, and vicea versa. The peripheral nervous system has sensory nerous receptors.

The peripheral nervous system

The peripheral nervous system lacks the protection that the central nervous system, unlike the CNS it has no skull or vertebral column.

The peripheral nervous system is divided into the autonomic nervous system, and the somatic nervous system. The somatic system can be controlled voluntarily. The autonomic nervous system has been described as ‘self regulating’.

The autonomic nervous system is divided into sympathetic and parasympathetic functions.

The PNS has mechano and nocioceptors. The nocioceptors are also known as ” pain receptors”. The proces sis called ” nociception”. Nocioceptros were discovered by Charles Scott Sherrington in 1906. Sometimes pain is referred to as the perception of pain. As an example the nocioceptors on the reception of pain takes the signal through the spinal cord to the brain.

Once the pain signal reaches the spinal cord, the response is taken over by the efferent, or theneurons that take signals away from the CNS towards the muscle.

By contrast the afferent neurons are sensory neurons that carry nerve impluses from sensory stimuli towards the CNS.

The sympathetic nervous system can communicate with many different things at once, where as the parasymmpehtic tends to communicate more dierectly ?

The sympathetic nervous sytem is the bodies involunatry response to dangerous or stressful situations. We are all familiar with the symptoms of sympathetic nervous system activity: our heart rate increases, our breathing increases, and we may sweat.

The physiological response of the sympathetic of the nervous system for low level every day threats we exeprience has been compared to creating the same reaction as when we’re in survival.

A involuntary and rapid response to pain are called innate, or intrinsic reflexive actions. There’s also learned, or acquired reflexes that are built by experience.

Stretch receptors in a muscle are called ” muscle spindles”. Their role is to detect changes in the length of a muscle. These spindles communicate with the CNS via afferent nerve fibres. When these spindles are stimulated it triggers a contraction in the muscle to prevent it from stretching further.

Some neurons have channels that open when the membranes are stretched. This is called “mechanically gated” channels. A physical stimulus may do this.

There’s lignand gated channels that open when histamine or potassium ions which are released by dmaged tissues bind to the receptors.

Stimuli in the PNS is converted into electrical energy. At a certain level of electrical energy, an action signal

In the PNS there are:

satellite cells
schwann cells

A resting neuron is

In the perihperal nervous system, which is one of the two components that make up the nervous sytems in bilateral animals we’ve got satelite and schwann cells, which is the connectin between the braind and psinal cpord to the rest of the body.

The CNS is protected by the vertebral column, and skill, and blood-brain barrier.

The brain is resource intesive and consumed about 20% of the energy through it’s activity of th ebody.


Also called the gustraotry sense, or gustatory.


THe visual sense is the dominant sense in humans. Around the eyes the eye brows are designed to keep liquid and other things out, as are the eyelashs. The eye is a ball, but we can only see approximately one sixth from the front. The wall is made up of the fibrous, vascular, and inner layers.

The posterior chroid supplies all of the layers with blood. There is the ciliary body, the muscle that surrounds the lens. When light goes through the pupil the disc focuses that light, and protjeccts onto the retina which is the inner layer of the back of the eye ball. The retina’s have photorecetpors which convert the light energy to electrical signals to be transported through the brain.

The photoreceptors are called rods and cones. Cones detect colour, and fine detail. The rods don’t sense colour ?, instead the sense black and whitr The rteina has two layers, the inner layer is neurons. It contains bipolar neurons, and ganglion neoruons. The cones have red, blue and green senstiive types? Rods connect to ganglion cells in many to one which makes it difficult for the ganglion cells to ascetsain whihc rod sent what information.

Each cone connects to a ganglion cell one on one.


An adult human contains 206 bones, reduced from 270 bones at birth as some get fused together. Your bones are made of connective tissue. The bonses are divdied into the axial bones, which occur along the bodies vertical axis, The appendicular bones are the ones that make up everything else.

Bones are also classidied by shape. There are long bones.

The short bones are normally cube shaped.

There are thin bones which normally protect something underneath.

The irregular bones tend to be uniquely shaped.

Despite ths shape of the bone the internal structure is similiar. They all have adense , compact external layer called corticol bone, which is around a spongy bone that looks honeycomb shape. The honey comb is made up of a material called trabeculae. The trneculase is where the bone marrow is. Bone marrow can be red bone marrow, or yellow bone marrow.

The red marrow is meant to be where we make cells, where as the yellow is where we store cells as fat.

The larger end of the bone. It almost looks like the end of the prototypical ” dog” bone, or like bookends are called epiphyses, they surround a caviity called the medullary caivty which has yellow marrow.

The bones are porous. The osteocytes form the cells of the tissue of the bone. They form what we call the mineral matrix of the bones. Inside the compact part of the bone is like tubes running in a tree trunk. These tubes are called lamellae. From lamellae to lamellae the fibres ? run one way and then the other which helps resist the torsion stress that gets placed on bones.

In the middle of the lamellae runs nerves and blood vessels in a central canel.

The bones store calcium and phosphate ? The bone marrow also makes the red blood cells. This is called hematopoiesis. ? Humans make over two million new red blood cells every second. Stop

In contrast to osteoblasts, there are osteoclast cells in the bones. They are responisble for bone reabosbtion, and to regulate the level of calcium. This is sometimes called “bone remodelling”. This process of bone reanorbtion is sometimes called ” resorption”. Exercise is often thought of as being potentially a way to stimulaete bone remodelling.

We know from experiments in space that when there is less gravity the osteoblasts don’t contribute as much to bone formation, and the osteoclasts are more active in their orle of bone resorption.


The joints are a junction, or wthe articulation of where two bones meet. Cartlidge sis the substance that covers the surface of a bone at the joint.

Ligaments and tesnsons are type of strong and dense connective tissue. Ligaments connect bones to bones. Tendons connect muscles to bones.

The first type is called synarthroses. This are sometimes thought of as being syarthoses, because they have little or no movement. The sutures of the skull are a good example.

There’s amphiarthroses joints. Amphi means stiff and slightly movable. The vertebral joints are an example.

There’s synovial joints, sometimes called diarthroses. There’s a ball and socket synovial joint. There’s shoulder and hip joints as an example.

Hinge joints, elbows and knees are an example. They move in one dimension, like a door hinge. In the joint is a fluid called synoval fluid that lubircates the ojints, it’s in the synoval capsule that surrounds the joint. There is also something called articular cartlidge, specifically called hyaline cartlidge. All cartlidge lacks blood vessels.

One common condition is when the joints inflame is called arthritis. The suffix -itis designates inflammation, and arth as a joint.