the nervous system - CNS Flashcards
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
sensory perception
an awareness of internal and external environment
cognitive functions
ability to process thought, encapsulating memory, learning, comprehending, speaking etc.
motor functions
control of movement
regulatory functions
-emotions
-appetite
-heart rate
-breathing
-temperature
nervous system consists of:
-central nervous system CNS
-peripheral nervous system PNS
autonomic AFFerent
travel via the sympathetic and parasympathetic nerves
-like the sensory neurone
autonomic EFFerent
travel via the sympathetic and parasympathetic nerves
-like the motor neurone
ANATOMICALLY, the central nervous system consists of:
-brain (1.4kg)
-spinal cord (C1-L1/2)
FUNCTIONALLY, the central nervous system:
-receives input
-integrates stimuli
-triggers a response to stimuli
how is the CNS protected from damage ?
-bones
=skull (cranial cavity)
=vertebrae
-meninges
=membranous coverings of the brain
and spinal cord
3 layers of the brain (outside to inside)
-cerebral cortex
-limbic system
-central core
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
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
central core (brain stem, thalamus & cerebellum)
-in ALL vertebrates
-controls basic functions
-little learning, but basic functions to survive (e.g. heart + breathing rate)
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
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
