Nervous System Flashcards
Homeostasis
- maintaining constant internal environment despite changes in the external environment
- eg: we get cold so we shiver, we get hot so we sweat
Different types of receptors (5)
Chemoreceptors –> chemicals (eg: taste buds on tongue)
Mechanoreceptors –> pressure, vibrations and touch (pressure receptors in skin)
thermoreceptors –> temperature (hot and cold receptors in skin)
photoreceptors –> light (rods and cones in retina)
pain receptors, nocireceptors –> cell damage/excess heat
Nervous System breakdown
CNS (body master control unit)
1. brain and spinal cord
PNS (body link to the outside world)
1. autonomic NS (internal stimuli, involuntary process)
- sympathetic NS (fight or flight)
- parasympathetic NS (rest + digest)
- somatic NS (external stimuli, voluntary movements, sensory info from organs to CNS and then to muscles)
- sensory input (Afferent)
- motor output (Efferent)
3 functions of the nervous system
1) Sensory input from sensory receptors (PNS) is transfered to CNS.
2) integration and intepretation in the CNS
3) Conduction of signal from CNS to effector cells, muscles + glands which carry out the bodys responses (PNS)
SENSORY INPUT PNS –> INTEGRATION/INTREPRATION CNS –> MOTOR OUTPUT PNS
Dendrites
- INPUT zone where cell recieved neural information
- recieve info from environment/other neurons
- conduct nerve impulses AWAY from cell body
Cell bodies
- contains the nucleus
- recieve, sort, priritize neural information
Axon Hillock
- act like a switch
- trigger electrical impulses to move to the axon
Axon
- OUTPUT zone
- conducts nerve impulses toward axon terminal
- long cord like extension of cytoplasm, conducts nerve impulses away from cell body
- larger diameter of the axon the faster the speed of nerve impulse
Nodes of ranvier
Allow diffusion of ion
Axon terminal
- At hthe end
- forms junctions with other cells
- store NT chemicals which control transfer of neural info btwn neurons
Myelin sheath
- insulation for neurons
- made up of schwann cells
- nerve impulses move faster along myelinated nerve fibres than unmyelinated
Neurilemma
- surrounds the axon, on top of myelin
- formed by schwann cells and promotes regeneration of damaged azons
White/Gray matter and neurilemma etc
- Just because there is a myelin sheath doesn’t mean there is a neurilemma
White matter in brain have myelin
Gray matter dont have myelin (in spinal cord)
White and gray matter both odnt have neurilemma which means damage to CNS is permnant
Order of axon, myelin etc
Innermost –> outermost
Axon > myelin > neurilemma > Schwann
Schwann Cell
Produces the myelin sheath
3 groups of neurons
Sensory neurons (afferent neurons)
- relay info/stimuli thats received by sensory receptors about external/internal environment
- cell bodies of sensory neurons are located in clusters called ganglia (outside the spinal cord)
2) interneurons (association neurons)
- link neurons to other neurons
- integrate + interpret sensory info + connect sensory neurons to outgoing motor neurons
- only in brain + spinal cord
3) motor neurons (efferent neurons)
- relay information to the effectors (cell/organ that responds to stimulus)
Glial cells
non conducting cells that are Support cells
- support neurons structurally
- deliver nutrients + remove waste
- repair neurons in PNS
- insulate neurons
Glial cells in the PNS
Schwann cells
- axon > myelin > neurilemma
- has a nucleus that directs growth of myelin
- gaps btwn schwan cells are nodes of ranvier
Glial cells in the CNS
1) oligiodendrocytes
- wrap around neurons making insulating sheaths
- made up of myelin (white matter)
- astrocytes
- provide structure + metabolic support
Reflex Arc
- reflexes involuntary + unconscious
- neural circuit that travels through spinal cord and provides a framework for reflex action
sensory receptor –> sensory neuron –> interneuron in spinal cord –> motor neuron –> effector
action potential
change in electrical potential associated with passage of an impulse
voltage gated channels, ligand gated channels and mechanically gated channels
voltage gated: open at certain membrane potential and close at others (eg: NA channels open around -55mV)
ligand gated channels: open when a specific NT latches
mechanically gated channels: open in response to physically stretching the membrane
If action potentials are all the same how do we know the strength of a stimulus?
1) More sensory receptors fiting, mean more action potentials = stronger stimulus
2) higher frequency of firing = stronger stimulus
Salatory conduction
node to node conduction. conduction that happens myelinated axons.
1) saves energy by decreasing use of sodium potassium pump
2) its faster which allows organism to react faster
