8 The Central Nervous System Flashcards
Q: What is the nervous system for? 2 divisions? Examples (2,3).
A: Mainly communication
- bodies and external environment (somatic senses and special senses)
- within our bodies (higher cognitive function and movement and visceral sensation)
Q: What is meant by afferent? efferent?
A: periphery to centre, centre to periphery
Q: What doesn’t make a species smarter? (2) What does make a difference?
A: more neurons, larger brain
cortex structure eg smooth in mice but human= v folded= larger SA
-> number of cerebral cortex neurons makes a difference
Q: What is brain morphology related to? Why is the brain described as an onion?
A: function
has layers with increasing complexity
Q: What makes up the brain stem? What is above it? Describe each component.
A: top
-midbrain: has lots of of nuclei and groups of neurons with different functions including substantia nigra= degenerates in parkinsons disease
-pons: contains grey nuclei and connects 2 halves of cerebellum
-medulla oblongata: similar structure to spinal cord with the grey and white matter- just larger
bottom
diencephalon
Q: Planes:
sagittal?
transverse?
coronal?
References:
cranial? caudal? anterior? posterior? proximal? distal? lateral? medial?
A: -longitudinal that divides the body into right and left parts
- aka horizontal= separating top and bottom (inferior and superior parts)
- dividing the body into dorsal and ventral parts (front and back)
-towards head
-towards feet
-ventral/front
-dorsal/back
-towards centre (used in reference to relative locations of parts or places on the limbs)
-away from (used in reference to relative locations of parts or places on the limbs)
-outwards from midline
midline
Q: What is the spinal cord? Protection? What does this structure also provide?
A: thin column of nervous tissue
well protected within bony vertebral column= made of a stack of vertebrae (form vertebral canal within where spinal cord sits)
flexibility/movement
Q: When vertebrae are stacked, what do they form? Function?
A: form intervertebral foramen (between them)= holes
spinal nerves emerge from them
Q: Where is the barrier between the CNS and the PNS?
A: intervertebral foramen where the spinal nerves emerge
Q: How many nerves do we have? Relationship to spinal cord? exception?
A: 31 pairs
come out below corresponding vertebra except in cervical tract where we have 8 nerves but 7 vertebrae
Q: Length relationship between spinal cord and vertebral column? means that? Results in? (2)
A: spinal cord is shorter than vertebral column (ends around L1/2) -> so there is some empty space at bottom (lower nerves need to travel down a little to reach their corresponding vertebra)
results in lumbar cistern = subarachnoid space in the lower lumbar spinal canal
cauda equina= only have fibres and no spinal cord (bundle of spinal nerves)
Q: What’s handy about space in lower vertebral column? How? Benefit?
A: when we want samples of cerebrospinal fluid that fills space
can insert needle between L3 and L4, 4 and 5
-> take sample without risking damage to the spinal cord itself
Q: How does the spinal cord vary in thickness? (4) Why?
A: cervical (enlargement)
thoracic
lumbar (enlargement)
sacral
innervate upper and lower limbs respectively
Q: What does each spinal cord segment innervate?
A: particular skin area- dermatome
Q: Describe a spinal cord cross section structure.
A: REFER
groove at front and back
symmetrical
dorsal and ventral rootlets coming out
(have lump = dorsal root ganglian)
white matter on outer part
grey matter = core where cell bodies are-> has dorsal horn (2 of them) and 2 ventral horns
central canal right in centre= small and fluid filled
dorsal median sulcus
ventral median fissure (longer)
Q: What’s in the dorsal root ganglion?
A: cell bodies of the sensory neurons are
Q: What happens in dorsal and ventral horn? Direction of information travel?
A: dorsal is where sensory neurons come in and synapse with inter neurons with in (go to brain)
ventral contains cell bodies of motor neurons
out from ventral horn and in from dorsal horn
Q: What are the functions of the spinal cord?
A: Connects the PNS and ANS to the brain
Carries sensory signals to the brain
Carries motor signals to the muscles
Coordinates reflexes- some information is processed at level of spinal cord without reaching brain
Q: Give an example of how the spinal cord coordinates a reflex.
A: patellar reflex
hit ligament on knee-> stretch muscles-> detected by stretch receptors -> causes muscle innervation
- motor neurones causes contraction or quadricep muscle
- sensory neurones synapses with interneuron in grey matter= inhibitory -> motor neuron inhibits hamstring muscle contaction
KICK FORWARD
Q: What 2 structures make up the cerebrum?
A: cerebral hemisphere
diencephalon on the brain stem
Q: What is the brain stem a continuation of? Why is lethal to it? why? Example.
A: spinal cord
tumours/lesions - as the brain stem has vital functions
can lead to locked in syndrome
Q: What makes the diencephalon? Where? (3)
A: made of hypothalamus and thalamus above
- thalamus= deep inside middle of brain
- hypothalamus is just below slightly forward
- behind optic chiasm
Q: Where is the pituitary gland?
A: comes off hypothalamus, connected by infundibulum (funnel shaped)
Q: What can be seen of the hypothalamus when looking at it from below? Blocked by? What is the hypothalamus part of?
A: mammillary bodies
optic chiasm and pituitary gland
diencephalon
Q: What runs through the brain stem? What does it contain?
A: All sensory and motor fibres that connect the cerebrum, the cerebellum and spinal cord run through it
Contains the nuclei of 10 of the cranial nerves (III to XII)- their origin
Q: What is the brain stem responsible for? (6)
A: control of many vital functions such as: breathing, heart rate/blood pressure, swallowing, balance etc.
Responsible for defensive reflexes (cough, gag, sneeze…)
Involved in sleep-wake cycles, alertness and consciousness
Q: What is the function of the hypothalamus? (5) Called?
A: integration hub
Regulates temperature, hunger, thirst, hormone (connected with pituitary) and autonomic function (homeostasis)
Q: What is the function of the thalamus? (4)
A: integration centre for somatic and special senses information and projection to cortex <= sensory neurons
Involved in emotional status, consciousness, appropriate motor response.
Q: What is the largest part of the cerebral hemispheres? What does it also contain? Structure of this component? (5) 2 umbrella structure names? connected to? (3) What is in the middle of the 2 symmetrical parts?
A: cortex
grey nuclei deeper down: basal ganglia
- caudate (head and tail)
- globus palidus
- putamen
- nucleus accumbens
- amygdala
Caudate + Putamen = Corpus Striatum - connected to cortex, thalamus, nigra
Putamen + Globus Pallidus = Lentiform nucleus
thalami (of the diencephalon)
Q: What is the function of the basal ganglia? (3)
A: Control of movement:
facilitating voluntary movement, inhibiting unwanted or inappropriate movements, “fine tuning”
Q: Cerebral cortex. Thickness? Organisation? How is it split up? (3) Names of the sections? (4) How much is exposed?
A: -2-4mm of grey matter and white matter below
- gyrus and sulcus (invaginations)= increase SA
- by fissures= deep sulci
- –longitudinal (separates left and right hemispheres)
- –central fissure (front and back separation)
- –lateral fissure (top from below)
- frontal
- parietal
- temporal
- occipital
30% roughly and 70 in within the folds
Q: Name and describe the cortical functional areas. (12)
A: REFER
- primary motor cortex: first impulse for movement start
- primary somesthetic cortex: somatic senses eg temperature, pain
- primary visual cortex: receives visual signals
- primary auditory cortex: receives auditory signals
- primary gustatory cortex: receives taste signals
- motor association area: neurons plan programme for the contraction of muscles to get response you want
- somesthetic association area: interprets sensory information and make cognitive sense of it
- visual association area: recognises faces and familiar objects
- auditory association area: recognises signals received as spoken words, music etc
- prefrontal cortex: personality/sense of our relationship with world
- broca area: generates motor programme for all muscles involved in speech (on dominant side of brain = usually L)
- wernickle area: responsible for recognition of speech and written language (on dominant side of brain = usually L)
primary= received association= made sense of
Q: What is the structure of the cortex?
A: majority is made of 6 layers where cells are distributed throughout
it is also somatotopic= point-for-point correspondence of an area of the body to a specific point on the central nervous system
-> both somatic and motor parts have map of our body
Q: What makes up the limbic system? (4) What is it to do with? (4)
A: -Hippocampus,
- Amygdala (at end of caudate gyrus)
- Olfactory bulbs
- Cingulate gyrus (groove between the left and right hemisphere)
- motivation
- instinctive behaviour
- emotion
- memory
Q: Describe the hippocampus. Important for? (2)
A: part of cortex which is tucked underneath the temporal lobe
memory and learning
Q: Where is the cerebellum? attached? Structure? (4)
A: attached to brain posteriorly (in occipital area) by 3 pairs of peduncles
- Grey cortex (with deep parallel folds, folia)
- deeper white matter, with nuclei
- Two hemispheres divided in lobes
- central vermis
Q: What does the cerebellum receive information from? (3) Include function.
A: - vestibular system for balance
- spinal cord and muscles of locomotion, posture; muscle tone
- Motor cortex and thalamus for learned movements (eg manual skills, trajectory, timing, speed and force)
Q: What can lesions in the cerebellum lead to?
A: ataxias= coordination of movement is disrupted
Q: Draw a diagram showing the structure of the white matter of the cerebellum (4). Fibre type?
A: between the hemispheres = saddle shaped fibres = commissural fibers (corpus callosum)
within the hemispheres= association fibres of varying lengths
projection fibres from within brain stem to edge of white matter
projection fibres= spread in cortex to make corona radiata and pass from cortex through white area called internal capsule, down through brain stem to spinal cord
all are myelinated fibres= quick in communication
Q: What protects the brain? (2) Label. (6) 7 other structures.
A: cranium
- top/ upper part is often the calvarium
- separate set of bones seen for base of skull from above
REFER
- frontal
- sphenoid
- temporal
- parietal
- occipital
- ethmoid
- foramen magnum= lower part of medulla goes
- posterior cranial fossa= cerebellum lies
- jugular foramen
- carotid canal
- middle cranial fossa= temporal lobe sits
- anterior cranial fossa= where frontal cortex sits
- sella turcica (hypophyseal fossa)= where pituitary sits
Q: Aside from bone, what protects the brain? Describe. (5)
A: meninges= layers of connective tissue below skull
dua mater= tough one, fibrous and thick, made of 2 layers which can separate- periosteal and meningeal (forms sinuses between)
arachnoid mater= v thin, web like structure, forms subarachnoid space below which allows blood vessels to run, area is filled with CSF
pia mater= v thin and follows all the gyrae
arachnoid villus= arachnoid mater layer pierces through dura mater and into (sagittal) sinus
dura mater does not follow brain shape, only fissures- it goes in to form scythe= falx cerebri= separates both hemispheres
Q: What specific structure does CSF fill in the brain? Describe.
A: ventricular system
REFER
(counts as 1 and 2) lateral ventricles- anterior, posterior and inferior horn
interventricular foramen connects it to third ventricle
3rd= lies between thalamus
aqueduct connects to 4th ventricle
4th= between brain stem and cerebellum -> communicates with subarachnoid space
Q: What produces CSF? where? How much a day? CSF space? meaning?
A: choroid plexus in all ventricles- lots of capillarires covered in ependymal cells (ones that lines ventricles)
around 500mL
whole CSF space is only around 150mL - just means it gets turned over several times a day
Q: Describe the circulation of CSF.
A: circulates: lateral ventricles, down from interventricular foramen. 3rd, aqueduct, 4th, subarachnoid space, arachnoid villi of dural vinous sinuses, venous blood, heart and lungs, arterial blood, reenters lateral OR 3rd OR 4th ventricle’s choroid plexuses
Q: What is the composition of CSF? (7) Look?
Na+ K+ glucose protein Ca2+ Cl- pH
A: is an ultrafiltrate of plasma with major differences
Composition similar to plasma (high Na+, low K+) but: Lower glucose (2/3) Much lower protein (200x) Lower Ca2+ Higher Cl- Slightly lower pH (7.33)
clear and colourless
Q: What are the functions of CSF? (5)
A: cushioning
nutrition
removing waste
Immune cells
Diagnostic- if RBC in it= could be sign of haemorrhage
