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. ?