Nervous Control Flashcards
What is the central nervous system made up of ?
The brain and the spinal cord
What is the peripheral nervous system made up of ?
made up of pairs of nerves originating from the brain or the spinal cord.
what is the motor nervous system divided into ?
the voluntary nervous system
the autonomic nervous system
What is the autonomic nervous system divided into ?
the sympathetic nervous system
the parasympathetic nervous system
what is the role of the sympathetic nervous system ?
stimulates effectors
speeds up activity
preparation for stressful activities ‘fight or flight’
increase heart rate
dilate pupils
inhibit activity of intestines and stomach
What is the role of the parasympathetic nervous system ?
inhibits effectors slows down activity
Controls activities at rest
conserves energy and replenishes the bodies reserves
slow heart rate
constrict pupils
stimulate activity of stomach
What 3 neurones does a REFLEX ARC involve ?
Sensory neurone
Intermediate neurone
Motor neurone
What are the main stages of a spinal reflex arc when touching a hot object ?
Stimulus is the heat from the hot object
Receptors detect temperature change in the skin and generate a nerve impulse.
Sensory neurone passes the nerve impulse to the spinal cord.
Intermediate neurone links the sensory neurone to the motor neurone in the spinal cord.
Motor neurone carries the nerve impulse from the spinal cord to a muscle in the upper arm.
The muscle in the upper arm which is stimulated to contract.
What is the effector in a simple reflex arc when touching a hot object ?
the muscle in the upper arm which is stimulated to contract.
What is the response in a simple reflex arc when pulling the hand away from the hot object ?
pulling the hand away from the hot object.
What is the role of reflex actions ?
Avoiding damage to tissues and prevents injury
Used to escape from predators
Describe the importance of REFLEX ARCS
protect the body from harmful stimuli
Make survival more likely
What is resting potential ?
In a resting axon (one that is not transmitting impulses), the inside of the axon always has a negative electrical potential compared to outside the axon.
Describe the structure of a neurone.
They have :
a cell body : contains a nucleus with large amounts of Rough ER associated with the production of neurotransmitters.
Dendrons and dendrites :This means they can connect to many other neurones and receive impulses from them, forming a network for easy communication
An axon : a single long fibre that carries nerve impulses away from the cell body
A myelin sheath and Nodes of Ranvier - allows nerve impulses to travel by saltatory conduction which speed up the rate of transmission.
What is the numerical value for the resting potential of the axon membrane ?
-70mv
Explain how resting potential is maintained in a neurone.
Sodium-potassium pumps are present in the membranes of neurones
These pumps use ATP to actively transport 3 sodium ions out of the axon for every 2 potassium ions that they actively transport in.
This means that there is a larger concentration of positive ions outside the axon than there are inside the axon
The movement of ions via the sodium-potassium pumps establishes an electrochemical gradient.
The cell-surface membrane of neurones has selective protein channels that allow sodium and potassium ions to move back across the membrane by facilitated diffusion.
The protein channels are less permeable to sodium ions than potassium ions
This means that potassium ions can diffuse back down their concentration gradient, out of the axon, at a faster rate than sodium ions.
What is the defintion of an Action Potential ?
The change that occurs in the electrical charge across the membrane of an axon when it is stimulated and a nerve impulse passes.
also known as a ‘wave of depolarisation along the axon membrane’
What causes the production of an action potential ?
a stimulus
Explain how an action potential is produced when a stimulus arrives at a resting neurone.
Sodium ion channels in the axon membrane open
Sodium ions pass into the axon down the electrochemical gradient.
This reduces the potential difference across the axon membrane as the inside of the axon becomes less negative (depolarisation)
Depolarisation triggers more channels to open, allowing more sodium ions to enter and causing more depolarisation (positive feedback)
If the potential difference reaches around -55mV (known as the threshold potential), many more channels open and many more sodium ions enter causing the inside of the axon to reach a potential of around +40mV
An action potential is generated
The depolarisation of the membrane at the site of the first action potential causes sodium ions to diffuse to along the axon, depolarising the membrane in the next section of the axon and causing sodium ion voltage-gated channel proteins to open there. (conduction)
What happens during repolarisation ?
Voltage gated sodium ion channels close
Voltage gated potassium ion channels in the axon membrane open.
This allows the diffusion of potassium ions out of the axon, down their concentration gradient
This returns the potential difference to normal resting potential (-70mv)
What is Hyperpolarisation ?
This is when the potential difference across this section of axon membrane briefly becomes more negative than the normal resting potential
What is the Refractory Period ?
Once an action potential has been generated there is a period when sodium ions cannot move into the axon because the voltage gated sodium ion channels are closed. (unresponsive)
During this time it is impossible to generate a new action potential.
(a period of recovery)
What is the importance of the Refractory Period ?
Ensures that an action potential is propagated in one direction only
Produces discrete impulses
It limits the frequency of impulses that can pass along an axon in a given time.
What is the ALL-OR-NOTHING LAW ?
An impulse (action potential) is only transmitted if the initial stimulus is sufficient to increase the membrane potential above a threshold potential