CNS and PNS Flashcards
CNS
part of the nervous system which consists of the brain and spinal cord
bone
provides a strong rigid structure to protect the brain and spinal cord
cranium - brain, vertebrae - spinal cord
meninges
layers of connective tissue covering the brain and spinal cord
dura mater
tough and fibrous, attached to the skull closely but not so close fitting on the inside of the vertebral canal
arachnoid mater
loose mesh of fibres
pia mater
contains many blood vessels, sticks closely to the surface of the brain and spinal cord
cerebrospinal fluid structure
- clear watery fluid containing some cells and glucose protein fats salts
- occupies space between middle and inner layers of meninges
- formed from blood, circulates through CNS (cavities in brain and through centre of spinal cord) before reentering blood capillaries
CSF function
shock absorber, brain suspended in it, provides nutrients to and removes wastes from CNS
cerebrum
- thinking reasoning memory intelligence
- coordinating body’s voluntary activities in response to information from sensory receptors
- highly folded to increase SA
convolutions/gyri
rounded ridges formed by folding of cerebral cortex
sulci and fissures
shallow/deep downfolds between convolutions in cerebral cortex
grey matter made of
neuron cell bodies, dendrites, unmyelinated axons
basal ganglia
inner surface, consists of nerve cell bodies associated with control of skeletal muscle, plays a role in initiating desired and inhibiting unwanted movement
3 functional areas of cerebral cortex
sensory areas - receives and processes impulses from sensory receptors
motor areas - sends impulses to effectors via efferent pathway
association areas - intellectual, emotional interpret info from senses and make it useful
lobes
frontal - thinking, problem solving, emotion, personality
insula - recognition of different senses and emotions, addiction, psych disorders
temporal - processing and linking memories with senses/ auditory
occipital - vision
parietal - every other receptor
white matter
myelinated axons, fatty nature of myelin sheath causes white colour
tracts
myelinated nerve fibres between cerebral cortex and basal ganglia, make up white matter
- connect various areas of cortex within same hemispheres
- carry impulses between right and left hemispheres
- connect cortex to other parts of brain and spinal cord
nervous system
system involved with the control and coordination of the body
corpus callosum structure
wide band of nerve fibres that lie underneath the cerebrum at the base of the longitudinal fissure
corpus callosum function
nerve fibres in the corpus callosum cross between 1 cerebral hemisphere to the other so there is communication between the 2 hemispheres
cerebellum structure
under the rear of the cerebrum, surface is folded into a series of parallel ridges
cerebellum function
controls posture, balance, fine coordination of movement, receives sensory info from inner ear about posture and balance, and stretch receptors in skeletal muscles for info about length of muscles
all functions take place below conscious level, nerve impulses do not originate from it, can still move, jerky uncontrolled spasmodic movements
hypothalamus function
maintains homeostasis (constant internal environment), regulates autonomic, food water intake temp secretion of hormones and part of endocrine system
medulla oblongata stucture
continuation of spinal cord, extends from just above point where spinal cord enters skull
medulla oblongata function
automatically adjusts body functions as it contains control centres for basic functions necessary for survival
cadiac - rate and force of heartbeat
respiratory - rate and depth of breathing
vasomotor - diameter of blood vessels
other centres for reflexes like cough sneeze etc
influenced and controlled by higher centres of brain esp hypothalamus
spinal cord structure
passes through foramen magnum at base of skull, travels down body to 2nd lumbar vertebra
surrounded by vertebrae, meninges, but outer meningeal layer not closely attached to bone, instead there is a space filled with fat blood vessels connective tissue to provide padding to spinal cord and allow it to move when spine bends
grey matter surrounded by white matter - made of unmyelinated fibres and cell bodies
myelinated bundles of nerve fibres in white matter make up ascending and descending tracts
central canal contains CSF
spinal cord function
- ascending/descending: sensory/motor neurons carry impulses up/down spinal cord to/away from brain
- integrates spinal reflexes
neuron nerve fibre nerve progression
nerve fibres - axons and dendrites of neurons
nerve fibres held together in bundles of connective tissue, mulitple bundles join together to form nerves
PNS
part of the nervous system which connects CNS to receptors effectors glands
- nerve fibres arranged into nerves that arise from brain and spinal cord, carry info to and from CNS
cranial and spinal nerves
cranial - mostly mixed nerves (made up of sensory and motor fibres)
spinal - all mixed nerves
each nerve joined to spinal cord by 2 roots
ventral root - axon of motor neuron that has cell bodies in grey matter of spinal cord
dorsal root - axon of sensory neuron
dorsal root ganglion - small swelling in dorsal root, contains sensory neuron cell bodies
afferent division
carries impulses to CNS from receptors via sensory neurons
somatic - skin and muscles
visceral - internal organs
efferent division
carries impulses away from CNS to effectors
somatic and autonomic differences
autonomic/somatic
to glands, heart muscle, involuntary muscles/skeletal muscles
controls body’s internal environment/response to outside environment
acetylcholine and noradrenaline/only acetylcholine at effector
usually involuntary/usually voluntary
2 sets of nerve to target organ (para and sympa)/1 set of nerve to target organ
effect on organ to excite or inhibit/excite organ only
pre and post ganglionic nerve fibres from CNS to effector, synapse at ganglion/1 nerve from CNS to effector, no synapse at ganglion
parasympathetic
generally produces responses that maintain the body during relatively quiet conditions
sympathetic
tend to produce fight or flight responses to prepare body for strenuous physical activity
normal vs threatening conditions
normal: both S and P send out nerve impulses to internal organs to maintain stability of body functions (antagonistic)
threatening: S stimulation becomes dominant to provoke fight or flight response, prepares body for increased activity, increase movement increase alertness, think and act quickly
fight or flight response
pupils dilate
airways in lungs dilate, increase rate and depth of breathing
increase rate and force of heart contraction, increase blood pressure
blood vessels dilate heart liver lungs skeletal constrict everything else
liver converts glycogen to glucose, increase blood glucose level
adrenal medulla releases nor and adren, prolonging and intensifying these responses
increase secretion from sweat glands
