neuron and brain structure

NOT EVERYTHING. Slides have some labelling stuff you need to study too!

central nervous system (CNS)

• brain and spinal cord

• Integrates, processes & coordinates sensory data & motor commands

• Seat of higher functions:

  • Intelligence

  • Memory

  • Learning

  • Emotions

peripheral nervous system (PNS)

• everything but the brain and spinal cord

• Carries sensory information from receptors to CNS (TOWARDS midline to brain: Afferent division)

• Carries motor commands from the CNS to periphery (Efferent division)

• connects you to the outer world!

nerves of PNS

Cranial neves (comes off brain) and spinal nerves (comes off spinal cord)

simple parts of brain

• cerebrum

• cerebellum

• brainstem

where are the cell bodies and axons in your CNS?

• cell bodies in nuclei (collection of neurons together deeply inside the brain)

• axons in tracts (in the brain or spinal cord)

where are the cell bodies and axons in your PNS?

• cell bodies in ganglia (collection of cell bodies outside the spinal cord)

• axons in nerves (out the brain / spinal cord)

overview of PNS

• somatic (under conscious control)

  • sensory

  • motor

• autonomic (visceral / organ) (automatic)

  • sensory

  • motor

    • sympathetic 

    • parasympathetic

cells in the nervous system

• neurons 

  • nerve cells that conduct signals

  • the middle men (conductor). delivers a thought down to your body part to move it! delivers a feeling to the brain for processes

• neuroglia “glue”

  • are support cells for the neurons 

  • very important for metabolic functions!

neurons

• Neurons encode information and conduct it over considerable distances and transmit it to other neurons or various non-neuronal cells

• The brain has about 100 billion (10^11) neurons

• Neurons form connections to other cells via synapses

  • 10^15 synapses

  • Each neuron has about 100,000 connections with other neurons

synapse

• Point of contact of an axon terminal with another cell

• Transmits nerve impulse via neurotransmitter

what happens when Action Potential reaches synaptic terminal?

neurotransmitters released into synaptic cleft

how to tell the difference between sensory and motor neurons?

sensory neurons are unipolar or bipolar, have two axons, and transport signals from periphal to CNS. motor neurons are multipolar, have one axon and transport signals from CNS to peripheral

nucleus

A collection of nerve cell bodies within the central nervous system

tract

A collection of axons in the central nervous system

ganglion

A collection of nerve cell bodies in the peripheral nervous system. all sensory neurons live here

nerve

A collection of axons in the peripheral nervous system

neuroglia

Support cells for the neurons

• in PNS: Schwann cells and satellite glial cells

• in CNS: Astrocytes, Oligodendrocytes, Microglia, Ependymal cells

cells of the PNS

• satellite cells

• schwann cells

• nodes of ranvier

satellite cells

• cell in PNS

• surround sensory neuronal cell body

• supportive role (regulate neurotransmitters, O2, CO2)

schwann cells

• cell in PNS

• Myelinate peripheral axons (sensory and motor)

• One Schwann cell per myelinated segmentt

• the outside of a cell (plasma and membrane. inside of a cell; most but not all cytoplasm n all that got squeezed out) made of fat that wraps around an axon

nodes of ranvier

• cell in PNS

true or false: fat is a perfect insulator so the current will not leave the cell when going down the body. the signal also doesn’t leave thru the notes of ranvier because there are receptors also but there are also cells that will top up the signal so it’s boosted n proper and above threshold

true

cells of the CNS

• oligodendrocyte

• microglia

• neuron

• astrocyte

• ependymal

oligodendrocyte

• cells in CNS

• myelinates CNS axons

• provides structural framework

microglia

• cells in CNS

• removes cell debris, wastes and pathogens using phagocytosis (it eats it)

neuron

• cells in CNS

• kinda like a macrophage but theres no macrophages here cause the blood brain barrier so they have this instead. not as good as macrophages

• cortical neuron (CST motor neuron) = neurons of the cortex

astrocytes

• cells in CNS

• maintains blood brain barrier

• provides structural support

• regulates ion, nutrient and dissolved gas concentrations

• absorb and recycles neurotransmitters

  • communicates with other cells after an injury will go in and try to recycle/clean things up

• forms the scar tissue after surgery

  • but then when they don’t leave so it scars (glial scar).

  • the scar couldn’t regenerate and heal if they tried because of the glial scar blocking them

• communicate with the neuron itself and its little feets wraps around BV (capillary) super duper closely to each other that it forms a blood brain barrier (BBB), encasing the capillaries. makes it so things can flow between the brain tissue and the capillaries all willy nilly. the only way blood stuff can get through astrocyte to CNS is through a channel (BBB)

ependymal cells

• cells in CNS

• lines ventricles (brain) and central canal (spinal cavity)

• assists in producing, circulating and monitoring cerebrospinal fluid

• the epithelial layer that prevents ventricle fluid from getting into brain tissue/if a molecule needs to get into brain it’ll go through a channel in these cells.

• Regulates ions

CNS protection

• Meninges (membranes) – cover and protect the CNS

  • Dura Mater

  • Arachnoid Mater

  • Pia Mater

• CNS floats in cerebrospinal fluid

  • brain is sitting in a sac of water. water is CSF and it comes from blood. ependymal cells takes fluid (not blood or white cells) from BV in brain which is CSF. makes it so that your brain isn’t smacking against ur skull like crazy and hurting itself

dura mater

• “hard mother”

• top layer of meninges

• Tough outer layer

arachnoid mater

• “spider mother” — looks like a spider web

• middle layer of meninges

• CSF – cerebrospinal fluid

pia mater

• “soft mother”

• bottom layer of meninges

• intimate contact with brain tissues

calvaria

skull cap. on top on dura mater

sulcus of brain

brain valleys

gyrus / gyri of brain

the hills of the brain

the purpose of sulci and gyri

to increase surface area of brain, so more neurons can fit in your brain = more memory storage!

cerebrum

• Higher cognitive functions

  • thought, intellect, planning, creativity

  • where are uniqueness is. decision making, humour, personality, understanding language etc.

• Language and speech

  • formulation & comprehension

• Somatic motor function

  • regulates skeletal muscle activity

  • regulates and coordinates movement (basal ganglia — areas that regulate start and end of movement)

• Somatic sensory function

  • interpret stimuli from environment

• Regulates the emotional aspects of behaviour

where is cerebrospinal fluid found?

above pia mater, below arachnoid space

what is between the left and right hemispheres of the brain?

longitudinal (interhemispheric) fissure

poles of the brain

• frontal pole (anterior)

• temporal pole

• occipital pole (posterior)

• named after the bones they lie under

lobes of the cerebrum

• frontal

• parietal

• temporal

• occipital

what are the frontal and parietal lobes separated by?

central (rolandic) sulcus

what are the parietal, temporal, and part of the frontal lobes separated by?

lateral (sylvian) fissure

frontal lobe

• your uniqueness and creativity areas!

  • motor planning

  • thinking

  • planning

  • personality

• includes primary motor cortex (PreCG)

primary motor cortex (PreCG)

also known as the precentral gyrus

• neurons here (resides in the cortex) send action potentials out to spinal cord thru PNS to move body!

parietal lobes

• perception of self in space

  • where are we in the environment? and helps us understand that we are different fron our surroundings

• includes primary somatosensory cortex (PosCG)

primary somatosensory cortex (PosCG)

also known as the postcentral gyrus

• receives action potentials and sends it to parietals to processes what we are feeling

occipital lobe

vision

temporal lobe

• learning and memory hearing

true or false: the PreCG and PostCG’s areas for specific parts of the body are parallel to each other

true

cortex

grey matter (dendrites and neuronal cell bodies here). sends signals to medulla

medulla

white matter (axons here)

if axons are going to different places they have different _____

names

fibre tracts in the brain

• Association fibres

  • intrahemispheric connections (stays within their hemisphere — i.e. only in left OR right hemisphere)

  • short (goes from superficial to deep)

  • long (goes from anterior to posterior)

• Commissural fibres

  • interhemispheric connections aka crosses hemispheres — i.e., in BOTH hemispheres)

• Projection fibres

  • travel to and from cortex

right cortex controls ___ side of body and left cortex controls the ___ side of body

left, right

brainstem parts

• midbrain

• pons

• medulla (oblongata)

cerebellum

• Acts as a comparator – compares intended movement with evolving movement and corrects for errors

• Ensures movements are smooth, coordinated and purposeful (skilled)

• Regulates posture and balance (makes sure core is stable)

• Disease – cerebellar ataxia (intention tremor, lack of balance and coordination)

  • _____ picks which muscles to use and silents the rest, when you have ataxia the muscles aren’t silent and kinda move/tremor

true or false: practice makes your cerebellum work ratios of muscles and joints and all that better

true

brainstem

• 3 parts: Midbrain, Pons, Medulla

• Contains motor & sensory pathways connecting cerebral cortex to spinal cord

• Houses cranial nerve nuclei (origins of CNs)

• Contains Reticular Activating System – important for arousal of cortex & consciousness

  • adreanline released when we are awake — so u stay awake when you wake up and when you get scared

• Vital centres for regulating heart rate & breathing

• Centres for regulating swallowing & gag reflex

midbrain

• Substantia Nigra

  • regulates motor activity

  • neuronal degeneration → Parkinson’s disease

    • difficulty starting movement, okay moving, and diffiuclty stopping

• Relay centres for visual & auditory pathways

• Cranial nerves III & IV attached to it

pons

• ‘Bridge’ between cerebrum & cerebellum

• Cranial nerves V, VI, VII & VIII attached to it

medulla (oblongata)

• Contains vital cardio-respiratory regulatory centres

  • if something pushes on this it silences these and then u stop breathing ggs

• Cranial nerves IX, X, XI & XII

ventricles of brain

• lateral vetricles

• third ventricle

• fourth ventricle

function of brain ventricles

makes cerebrospinal fluid

blood supply to brain

• Anterior Cerebral Artery

• Middle Cerebral Artery

• Internal Carotid Artery

• Posterior Communicating Artery

• Posterior Cerebral Artery

• Basilar Artery

• Vertebral Artery

• circle of willis

Anterior Cerebral Artery

supplies midsaggital portion. frontal and parietal lobes

Middle Cerebral Artery

supplies lateral portion

Internal Carotid Artery

brings blood up to brain to supply front brain. becomes middle and anterior

Posterior Cerebral Artery

supplies occipital lobe and temporals

Basilar Artery

vertebral + vertebral arteries. supplies PCA

Vertebral Artery

comes from chest cavity in foramen magnum