Nervous System Flashcards
What are the three parts in response to change in environment?
Sensation- receptors detect change inside and outside body.
Integration-process info and determine appropriate response
Reaction- motor output- activation of muscles or glands by neurotransmitters
What is the purpose of the nervous system?
Used by animals to increase survival by responding to changes in environment
Any change in environment = STIMULUS
What are the 2 divisions of the nervous system?
Central - brain and spinal cord- protected
Peripheral- connects cns to limbs- not protected
What’s the difference between the endocrine and nervous system?
NS= fast acting, effects short lasting, info via electrical impulse ES= slower, chemical agents in blood to cells, lasts longer
The peripheral nervous system can be divided. What are the divisions?
Sensory division- conducts impulse from receptor to the cns, informs cns of the state of the body inside and out.
Motor division - conducts impulse from cns to effectors ( muscle and glands)
What are the other 2 divisions within the motor division?
Somatic- voluntary, conduct impulse from cns to skeletal muscle, results in a conscious action
Autonomic- involuntary, conduct impulse from cns to smooth muscle, cardiac muscle and glands, reflex action ( fight or flight)
What are the 2 types of nervous tissue?
Neurones- conduct impulse
Neuroglia- cells that provide physical support and regulate internal environment
What is a neurone?
Specialised to conduct info from 1 part of body to another.
Describe the structure of a neurone ?
Cell body= soma One or more slender processes Input region= dendrite Conducting component= axon Secretory output region= terminal endings
What is a dendrite?
Thin branched processes- main function to receive incoming signals.
Increase S A of neurone
What is an axon?
Transmit electrical impulse away from cell body.
Most neurones have a single axon( up to 1 meter long)
What is a Schwann cell?
Insulating lipid myelin sheath that surrounds axon.
Wrap round axon so tight ( up to 10 times) their cytoplasm is squeezed out leaving only cell memb and nucleus.
What are the spaces between the Schwann cells?
Nodes of ranvier- no myelin.
Impulse jumps from node to node
Describe the function of the sensory neurone?
Relay impulse from receptors to CNS
1 long dendrite carries impulse from recep. To cell body
1 short axon carries impulse from cell body to CNS
Describe the function of the motor neurone?
Relays message from CNS to muscle and organs
Impulse carried along many short dendrite to cell body
1 long axon carries impulse from cell body to effector cells
What are relay neurones?
Relay info from sensory to motor neurones
Many short dentrites and axons to carry nerve impulse
What are the characteristics of an axon?
Take info away from cell body Smooth surface - 1 axon per cell No ribosomes Can have myelin Branch further from cell body.
Describe the characteristics of a dendrite?
Bring info to cell body Rough surface - usually many dendrites per cell Have ribosomes No myelin Branch near cell body
Describe to process involved in the reflex arc?
Arrival of stim at receptor. Activation of sensory neurone-pass dorsal root- sensation relayed to brain via collateral- info processed in cns - pass ventral root and activation of motor neurone bring about response at effector.
Describe a reflex action?
Fast, automatic, act to protect body. Follows reflex arc pathway.eg hand over flame- innate response!!
What are the 2 ways neurones conduct information?
From 1 end of neuron to the other end- done electrically via action pot.
Across the space separating 1 neuron from another( space = synapse). This is done chemically via neurotransmitters
What is resting potential?
More positive ions outside the cell create potential difference of - 70mv
Generated by k ions moving down conc gradient by facilitated diffusion
Active transport used to move 3 Na ions out for every 2 K ions in. ATP required
What happens to the action potential when stimulus occurs?
Triggers threshold stimulus. Change in charge across membrane. Excites neurone cell causing Na channels to open.
Na ions diffuse down conc grad.
Make inside cell less negative.
What is depolarisation ?
If pot. difference across membrane = -55 mv more Na channels open
More Na ions diffuse into neurone
All or nothing response
What is repolarisation?
At a pot. diff of + 30 mv Na channels close and K ion channels open
K ions diffuse out do neurone down conc grad
Start to get neurone back to resting pot.
What is hyper polarisation?
K ion channels slow to close - slight overshoot where too many k ions diffuse out of neurone.
What is the refractory period?
After an action potential a neurone can’t be excited straight away
Channels are recovering and can’t open
Ensures action pot. don’t overlap.
How are action potentials conducted?
Unmyelinated- undergo continuous conduction
Myelinated- saltatory conduction (leaps)
Which has faster AP conduction, myelinated or unmyelinated axons?
Myelinated- jumps from axon to axon
Which would conduct AP faster, axon with large diameter or one with small diameter?
Large diameter.
How do AP pass from one neurone to another?
Via neurotransmitters eg. Acetylcholine
AP reaches nerve terminal and is converted to chemical signal
Describe process of synaptic transmission?
AP arrives at end of axon= synaptic knob- stimulates Ca ion channels to open and Ca ions diffuse into knob. Increase in Ca ions cause synaptic vesicles to fuse with pre synap memb causing relates of Ach into synaptic cleft(exocytosis). Ach diffuses across and bind to receptors on post synaptic memb. Na channels open starting an AP. Neurotran. Removed by enzymes, diffusion or reuptake.
