nervous Flashcards
(32 cards)
3 types of tracts of white matter
association tracts - contains axons conducting nerve impulses between gyri of the same hemisphere
commissural tracts - contains axons conducting nerve impulses between gyri different hemispheres (e.g corpus callosum)
projection tracts - contains axons conducting nerve impulses between the cerebrum and lower CNS (thalamus, spinal cord)
what are basal nuclei
3 masses of grey matter (caudate, putamen, globus pallidus) receive input from cerebral cortex and send output to motor neurons via thalamus.
functions to regulate initiation and termination of movement and cognitive processes (thinking, memory)
four modalities of somatic sensations
tactile (touch, pressure, vibration, itch, tickle), thermal, pain, proprioceptive
classification of receptors
microscopic structure: free nerve ending, encapsulated nerve ending, specialised cell
type of stimuli received: mechanical, chemical, pain (nociceptor), light
location of receptor/origin of stimuli:
exteroceptor - external stimuli (five senses, pressure, vibration, pain)
interoceptor - internal stimuli (usually not consciously perceived - doesn’t reach cerebral cortex)
proprioceptor - joints, tendons, body position, balance
types of graded potentials
receptor potential - causes release of neurotransmitter to first-order sensory neuron
Generator potential - if strong enough, generates an action potential in first-order sensory neuron
rapidly adapting receptors vs slow adapting receptors purpose
rapidly adapting receptors are more for communicating change in stimuli and will reduce nerve impulses if there is constant stimuli (e.g thermoreceptors may adapt rapidly in hot shower)
slow adapting receptors are for body position, pain and continue to stimulate nerve impulses with constant stimuli (e.g. proprioceptors tell us where our fingers are when typing without looking)
what is arcuate fasciculus and what happens if there is a lesion
bundles of axons (white matter) containing fibres which connect/allow for communication between lobes. (e.g between wernicke’s area and broca’s area in the temporal and frontal lobe)
lesion causes connection aphasia so there may be difficulty repeating phrases. can understand and talk separately but no connection between the two
touch and pressure have what type of receptors
encapsulated nerve endings which have myelinated axons because stimuli is constantly received
pain and temperature have what type of receptors
free nerve endings which have unmyelinated axons because stimuli are not constantly received
which root do sensory receptors pass through to get to the spinal cord
dorsal
in through the door, out the vent
dorsal towards brain, ventral away from brain
how fast are signals transmitted by pain and temperature receptors and touch and pressure receptors
pain, temp:
slow 1m/s because unmyelinated
touch, pressure fast 50 m/s because myelinated
receptor for pressure is called
pacinian corpuscle
receptor for touch is called
meissner’s corpuscle
what are the protective structures of the spinal cord
meninges: pia, arachnoid, dura mater
cerebrospinal fluid
vertebrae of vertebral column
fluid in the spine
interstitial fluid - between dura mater and arachnoid mater (sub dural space)
cerebrospinal fluid - between arachnoid mater and pia mater (sub arachnoid space)
orders of neurons
first order - sensory neurons to spinal cord via spinal nerves
second order - from spinal cord to thalamus (cross over here - decussate)
third order - from thalamus to primary somatosensory area
three pathways of sensory impulses to cerebral cortex
1.) posterior column - medial lemniscus pathway
2.) anterolateral (spinothalamic) pathway
3.) trigeminothalamic pathway
brief explanation of posterior column-medial lemniscus pathway
first order neurons have cell bodies in posterior root ganglion and axons which make up the posterior column.
they synapse with second order neurons whose cell bodies are in the medulla and axons cross over before entering medial lemniscus.
these synapse with third order neurons whose axons extend to primary somatosensory area of cerebral cortex
brief explanation of anterolateral spinothalamic pathway
first order neurons have cell bodies in posterior root ganglia, axons terminate in posterior gray horn where second order neuron cell bodies are.
second order neuron axons cross over to opposite side of spinal cord before ascending as the spinothalamic tract
they synapse with third order neurons in the thalamus which have axons projecting nerve impulses to the cerebral cortex
cuneate fasciculus part of posterior column transmits what type of nerve impulses and from where
touch, pressure, vibrations, conscious proprioception from upper limbs, trunk, neck and posterior head
gracile fasciculus part of posterior column transmits what type of nerve impulses and from where
touch, pressure, and vibrations from lower limbs, trunk
peripheral nerve endings of posterior column-medial lemniscus pathways vs anterolateral (spinothalamic) pathway
posterior column-medial lemniscus pathway: encapsulated nerve endings (touch pressure vibrations conscious proprioception)
anterolateral (spinothalamic) pathway:
free nerve endings (pain, temperature, itch, tickle)
where are cell bodies of lower motor neurons (LMN) and what are their function
cell bodies are found in the brain stem and spinal cord. All excitatory or inhibitory signals ultimately converge into the lower motor neurons so only LMN send output from CNS to skeletal muscle fibres
skeletal muscles of face and head, and limbs receive signals from where?
face and head receive signals from brain stem via cranial nerves
limb skeletal muscles receive signals from the spinal cord via spinal nerves
