the nervous system - CNS Flashcards by ellie lo

overview of nervous system

the nervous system detects + responds to changes inside and outside the body to maintain homeostasis (alongside the endocrine system)
-sensory perception
-cognitive functions
-motor functions
-regulatory functions

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sensory perception

an awareness of internal and external environment

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cognitive functions

ability to process thought, encapsulating memory, learning, comprehending, speaking etc.

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motor functions

control of movement

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regulatory functions

-emotions
-appetite
-heart rate
-breathing
-temperature

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nervous system consists of:

-central nervous system CNS
-peripheral nervous system PNS

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autonomic AFFerent

travel via the sympathetic and parasympathetic nerves
-like the sensory neurone

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autonomic EFFerent

travel via the sympathetic and parasympathetic nerves
-like the motor neurone

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ANATOMICALLY, the central nervous system consists of:

-brain (1.4kg)
-spinal cord (C1-L1/2)

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FUNCTIONALLY, the central nervous system:

-receives input
-integrates stimuli
-triggers a response to stimuli

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how is the CNS protected from damage ?

-bones
=skull (cranial cavity)
=vertebrae
-meninges
=membranous coverings of the brain
and spinal cord

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3 layers of the brain (outside to inside)

-cerebral cortex
-limbic system
-central core

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cerebrum (cerebral cortex & corpus collosum)

-cerebral cortex
=well developed in primates
=controls all the higher order
cognitive functions
=regulates complex processing
(motor control) and olfactory inputs

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limbic system (hypothalamus, hippocampus, amygdala & cingulate cortex)

-more developed in mammals than other animals
-regulates emotion + memory
=if we like, we remember it and do it
again
=if we don’t like, we remember it and
don’t do it again

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central core (brain stem, thalamus & cerebellum)

-in ALL vertebrates
-controls basic functions
-little learning, but basic functions to survive (e.g. heart + breathing rate)

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cerebrum

-largest part of human brain
-2 hemispheres
-gyri = elevated ridges
-sulci = smooth grooves
-fissures = deep grooves
-intelligence not directly linked to size, but surface area (more gyri)
-human brain has highest neuronal density in cerebral cortex
=highly myelinated neurones -> fast
neural networks

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cerebrum has 2 hemispheres, each divided into 4 lobes:

-frontal
-parietal
-temporal
-occipital

frontal lobe

primary motor cortex (motor homunculus)
-voluntary movements

parietal lobe

primary somatosensory cortex (sensory homunculus)
-(somatic sensation - touch / temp. /
pain + proprioception)
-taste area

temporal lobe

-auditory area
-olfactory area

occipital lobe

-visual area

cerebrum layers

-cerebral cortex
=outermost layer of GREY matter
(neuronal cell bodies
-cerebral medulla
=inner layer of WHITE matter
(myelinated axons)
-corpus collosum
=only connection between the two
hemispheres

motor nerve pathways

2 neurones carry motor impulses from the brain to the skeletal muscle
-upper motor neurone (UMN)
-lower motor neurone (LMN)
right cerebral cortex controls movement of left body and vice versa

upper motor neurone (UMN) - CNS

-cell body in motor cortex
-decussates (crosses) in the medulla oblongata
-descends in spinal cord

lower motor neurone (LMN) - PNS

-at appropriate level in spinal cord, UMN synapses with LMN -exits spinal cord -terminates at motor end plate of muscle fibre (NMJ)

sensory nerve pathway

3 neurones carry sensation from skin to brain -primary sensory neurone -secondary sensory neurone -tertiary sensory neurone right cerebral cortex sense left body and vice versa

primary sensory neurone - PNS

-somatic sensory receptors in skin; cell body in posterior root ganglion -enters spinal cord

secondary sensory neurone - CNS

-some secondary sensory nerves synapse and decussate immediately (in cord) -others synapse and decussate in medulla oblongata -travels to thalamus

tertiary sensory neurone - CNS

-synapse in thalamus -travels to somatosensory cortex

limbic system

-hypothalamus: regulates ANS, controls pituitary hormone release -hippocampus: memory -amygdala: aggression -cingulate cortex: emotional responses to sensory input

central core

-thalamus -brain stem -cerebellum

thalamus

-all somatic sensory input enters brain via the thalamus

brain stem

-midbrain -pons (reg. breathing) -medulla oblongata (reg. breathing/heart rate + many autonomic reflexes) -reticular formation (alertness during sleep)

cerebellum

-co-ordinates movement and posture

blood supply to the brain

-receives about 15% of the cardiac output (~750ml/min) -circle of willis ensures good blood supply -autoregulation

autoregulation

the ability of an organ to regulate its own blood flow to preserve ideal pressure and flow

ventricles produce cerebrospinal fluid (CSF)

-4 irregular shaped cavities within the brain, called ventricles -they produce and circulate CSF -CSF travels down the central canal (in the spinal cord) and back up the outside of the spinal cord and over the brain surface

purpose of CSF

-it is a clear, colourless liquid, its purpose is to: =cushion brain =deliver nutrients/remove waste =maintain constant pressure

the spinal cord

-extends below the medulla oblongata =humans: top of C1 to L1/L2 -spinal nerves enter/exit the spinal cord along its length -below spinal cord are peripheral nerves (PNS) to the lower body

spinal cord matter

contrasts brain matter arrangement -GREY matter is located CENTRALLY -WHITE matter SURROUNDS it