Lecture 1 Flashcards
CNS
- brain and spinal cord
- control centre
- major function - analyse info from sensory organs
- damage cause global effect on body
- nerve fibres cannot regenerate
PNS
- consists of everything else - cranial & spinal nerves
- major function - transmit sensory info to CNS ; pass out motor impulses to effector organs
- damage causes local effect on body
- nerve fibres can be regenerated
afferent
to carry towards
efferent
to carry away
Inputs
travel from sensors to the brain via afferent
Outputs
travel from brain to effectors along efferent
Somatic nervous system
- controls voluntary movements
- detects sensory stimuli: smell, taste, noise
- always causes an excitatory response
- single neuron b/w CNS & effector organ
- thick myelinated fibres
- function - posture & movement
Autonomic nervous system
- regulates involuntary movements
- detects sensory stimuli: blood pressure, pH, salinity
- excitatory or inhibitory response
- thick or thin myelinated fibres
- two neurons b/w CNS & effector organs
- functions - secretion & control of metabolism
Sympathetic nervous sytem
- mobilises body systems during activity
- action is a quick response
- raises sensory awareness
Parasympathetic nervous system
- relxes body by inhibiting high energy functions
- action is a slow response
- restores sensory awareness to normal level
Excitatory currents
those that prompt one neuron to share info to the next through an action potential
Inhibitory currents
reduce probability of such a transfer taking place
Dendrites
- carry incoming signals towards cell body
- afferent
- short, branched extensions of a nerve cell
- nerve cell have many dendrites
- branch near cell body
- myelinated
- ribosomes
- rough surface
Axons
- carry signals away from cell body
- efferent
- long thread like
- nerve cell has one single axon
- branch away from cell body
- myelinated or non-myelinated
- smooth
- no ribosomes
Sensory neurons
- external stimuli to internal electrical impulses
- long denrites, short axon
- cell body in dorsal root ganglion in SC
- soma outside CNS
- afferent pathway
- found in skin, eyes, nose, ears
Interneurons
- connect sensory & motor neurons
- communicat w eachother
- short dendrite, short or long axon
- entirely within CNS
Motor neurons
- conduct impulses to effector organs
- located in ventral root ganglion of SC
- efferent pathway
- short dendrite, long axon
- soma and dendrite within SC, axon outside
- mainly found in glands and muscles
neuronal pathway
- 3 major components : axon, soma, dendrite
- neurons receive signals from denrite
- travel via cell body to axon
- from axon signal goes to next neuron via synapse
Multipolar neurons
- most comon type or neurons
- most abundant in humans
- 3 or more protoplasmic processes
- one axon, many dendrites
- major neuron in CNS
Bipolar neurons
- two processes run in opp direction
- one axon, one denrite
- few in number; rare in humans
- found in retina of eye and olfactory system
Unipolar neuron
- only one protoplasmic process
- axon only
- mammals - afferent division of PNS
- dorsal root ganglion; cranial nerve ganglia
Neuroglia
- CNS
* astrocytes
* microglia
* ependymal - PNS
* satellite cells
* schwann cells
Astrocytes/ Satellite
regulate the external environment of the neurons in the CNS
Schwann cells
form myelin sheath -
1. schwann cell enevelops an axon
2. it then rotates around the axon, wrapping its plasma membrane around in successive layers
3. schwann cell cytoplasm forced b/w the membranes
4. the tight membrane wrappings form the sheath
myellin sheath
- fatty white substance
- surrounds long and large diameter axons
- protects, insulates, increases speed of signal
oligiodendrocytes
maintain and generate myelin sheath
Microglial cells
- most prominent immune cell in CNS
- first to respond when something goes wrong in the brain
- performs phagocytic function to get rid of neuron debris
- thorny processes
ependymal cells
- forms ependyma - thin membrane that lines the ventircles of the brain and central column of SC
- main function - secrete, circulate & maintain homeostasis of CSF
