The central nervous system Flashcards
what is the CNS comprised of?
brain and spinal cord
what protects the CNS?
bones
meniges
cerebrospinal fluid
what is the function of the cerebrospinal fluid?
protects- being a shock absorber
supports - brain floats in it
transports- nutrition and waste
what is the meninges comprise of?
Dura mater
Arachnoid mater
Pia mater
what is the dura mater?
a thick durable layer attached to the skull
What is the arachnoid mater?
attached to the dura mater to provide a cushion effect
what is the Pia mater?
thin membrane that follows the gyri and sulci
draw the diagram of the spinal cord ?
must include grey matter central canal which contain cerebrospinal fluid and white matter
what is a ascending movement ?
a sensory axon that carry a nerve impulse towards the brain
what is a descending movement?
motor axon that carry impulses away from the brain
what are neurons?
highly specialised cells that carry’s information form one part of the body top another
what do glial cells do ?
supports, protects, provides nutrition and insulates them from each other
what is an afferent neuron?
takes nerve impulses from the receptors to the central nervous system
what is an efferent neuron?
take nerve impulses from the central nervous system to the effector structure
what is an interneuron?
they link sensory neurons and motor neurons together
what are the four types of neuron ?
unipolar
bipolar
multipolar
pseudo-unipolar
what is the structure of a unipolar neuron ?
has on extension from the cell body to the axon terminal
what is the structure of a bipolar neuron ?
a distinct axon and have a dendritic fibre that is separated by a cell body
what is the structure of a multipolar neuron ?
have a single axon and several dendritic fibres
what is the structure of a pseudo-unipolar neuron ?
a single axon from a cell body which branches of into dendrites an axon terminals
what are propertise and characteristics of a dendrite ?
short and highly branched
synapses with other neurons or receptors
transmit the electrochemical impulse towards the cell body
what are propertise and characteristics of axon ?
Typically a single long nerve fibre
terminate at synaptic end bulbs
connects with muscles, glands and other neurons
what is the myelin sheath ?
a fatty white sheath that surrounds the axon on most neurons
what is the myelin sheath created by ?
schwann cells
what is a benefit of a neuron having a myelin sheath ?
transmission of nerve impulse occurs faster
what are the gaps between the sheaths called ?
the node of ranvier
what is a reflex ?
a rapid automatic response to a change in the internal and/or external environment
What is a spinal reflex ?
a reflex carried out by the spinal cord the message is not sent to the brain until after response meaning it is involuntary.
What is a reflex arc ?
-receptor detects a stimulus
-sensory neuron sends a message to the central nervous system
-message is passed on to either a motor neuron or interneuron
-motor neuron sends message to the effector
-effector carries out a response
- message is sent to the brain
what are the two types of relfex?
Innate
Acquired
what is an innate reflex?
a relex that is built in as apart of being a human eg suckling grasping
What is a acquire reflex?
a reflex that is learnt eg catching a ball
Describe the process of action potential ?
- Stimulus is applied – membrane becomes permeable and sodium moves into the cell causing depolarisation: an all or none response occurs if decrease is more than a 15mV (threshold) so more sodium ions are allowed into the cell
- Depolarisation – when action potential is created from sodium ions allowed into the cell
- Repolarisation – ion channels on the inside of the membrane allow potassium ions out: this restores the electrical balance
- Hyperpolarisation – returning to the resting membrane
potential there is more potassium on the outside than
sodium on inside: causes membrane potential to drop and then returns to normal state - 1-4 steps refractory period – the brief time during and after-action potential when the neuron cannot be stimulated
what is a saltatory conduction?
the process of nerve impulse moving down the myelinated axon by jumping from one node of ranvier to the next
Describe the process of transmission across a synapse?
- Membrane depolarises – the end of an axon, calcium gates will open, letting calcium ions enter the cell
- Synaptic vesicle release neurotransmitters – relay message between neurons
- Neurotransmitters bind with receptors – bind on the neuron (acetylcholine, dopamine, adrenaline)
- Excitation or inhibition – occurs depending on the neurotransmitter
* Excitation – sending message – nerve impulse is generated when sodium enters the cell and depolarisation occurs
* Inhibition – nerve impulse is not sent because potassium moves out of cell: hyperpolarisation is reached
What is the definition of homeostasis ?
the process by which the bodys internal environment is maintained at a steady state.
Define the term stimulus ?
a change in the internal and external environment
Define the term receptors ?
cells that detect a change
Define the term modulator ?
receives the message and coordinates a response
Define the term response ?
cause of action
Define the term effector ?
muscle or gland that causes a response
Define the term feedback ?
how the stimulus changes
What is the bodys optimum temperature ?
36.8
How is heat lost ?
-Evaporation: by sweat turning in to gas
-Convection: movement of air removes radiated heat
-Radiation: emissions of electromagnetic radiation
-Conduction: direct transfer of heat by contract
What are physiological response to hot and cold conditions ?
sweating
vasodilation
Vasoconstriction
shivering
piloerection
changes to the metabolic rate
What is sweating ?
when external temp is above 28 sweat is released by the sweat glands to cool the body through evaporation.
What is vasoconstriction ?
impulses from the hypothalamus via the sympathetic nerves cause smooth muscles in the arterioles in the skin to prevent heat loss through radiation
What is vasodilation ?
impulses from the hypothalamus via the sympathetic nerves cause smooth muscles in the arterioles in the skin to relax increasing blood flow and heat loss due to radiation
What is shivering ?
Continuous contraction and relaxation of the skeletal muscle no work is done so all energy goes towards heating up the body.
What is piloerection
hair standing up on end to trap heat