The nervous system Flashcards
Diagram to show structure of the nervous system
function of the nervous system
detect and respond to changes inside and outside of the body
two types of nervous tissue
neurones
neuroglia
neurones function
to generate anf transmit nerve impulses
what do neurones consist of?
Cell body and it’s processes: one axon and usually many dendrites
neurones are different structures depending on it’s function
Structure of the different neurones
what is an Action potential?
electrical impulse transmitted by neurons
what stimilis can action potentials be initiated in response from?
outside the body - eg. touch, light waves
inside the body - eg. change in the concentration of CO2 in the blood alters respirationm, a thought may result in voluntary movement
Relay neurones
a neurone which recieves an action potential, passes it on or sometimes redirect it. (short axon). only found in CNS.
interneurons
Carry electrical impulse from sensory neuron to motor neuron. only found in CNS.
why do neurons need a continuous supply of oxygen and glucose?
as they can’t divide. unlike many other cells, neurons can normally synethise chemical energy (ATP) only from glucose.
Cell bodies
form the grey matter of the nervous system. found in the periphery of the brain and in the centre of the spinal cord. Group of cell bodies are called the nuclei in the CNS and ganglia in the PNS.
Axon and dendrites
extensions of cell bodies and form the white matter of the nervous system. axons are found deep within the brain and in groups, called tracts, at the periphery of the spinal cord. They are referred to as nerves or nerve fibres outside the brain and spinal cord.
Axon
carry impulses away from the cell body and are usually much longer than the dendrites.
multipolar neuron
a type of neuron that possesses a single axon and many dendrites (and dendritic branches). the most common type of neuron. They are located in the central nervous system (brain and spinal cord) and in autonomic ganglia.
bipolar neuron
a neuron with only two extensions—an axon and a dendrite—that run from opposite sides of the cell body. Cells of this type are found primarily in the retina
unipolar neuron
the simplest class of neurons that exhibit a single extension that gives rise to branches, some of which are receptive (dendrites). they are located within the skin, joints, muscles, and internal organs.
schwann cell
nucleus of schwann cell is found on the axon of myelinated neurones. it produced myelin sheath.
Dendrites
many short processes that recieve and carry incoming action potentials towards cell bodies.
in Motor Neurons they form part of the synapses
in sensory neurons they form the sensory receptors that respond to specific stimuli
how does an Action potential travel through a neuron
There’s already a resting membrane potential between the outside (positive) and the inside of the neuron (negative). When the action potential enters the cell, it causes the sodium channels to open, which cause Na+ to enter the cell, which depolarises the cell. This causes the action potential to conduct along the axon. After the action potential is conducted along the axon K+ leaves the neurone to repolarise the cell and to restore the resting membrane potential.
Travel of Action potential diagram
Refractorary period
The neuron hyperpolarises to allow the neuron to restore membrane potential before allowing any other action potentials to be generated.
Saltatory conduction
in myelated neurones where the movement of ions across the membrane can only occur at the nodes of ranvier (where there is no myelin sheath), which causes the conduction of the action potential to ‘jump’ along the axon, which is a quicker conduction compared to no mylenated neurons.
Synapse process
the electrical action potential reaches the pre-synaptic bulb which causes the voltage gated calcium channels to open and allow ca2+ ion to enter. This causes vesicles containg chemical neurotransmitters to fuse with the membrane and leave the neuron and enter the synaptic cleft. via diffusion the neurotransmitters bind to receptors on the post-synaptic bulb and causes ligand gated sodium channels to open. this allows Na+ ions to enter the cell, causing the neuron to depolarise and generate an action potential.
synapse diagram
what are the three proctetive connective tissues?
Endoneurium
Perineurium
Epineurium
diagram of the protective connective tissues
Endoneurium
delicate tissue surrounding each individual fibre (chain of neuron)
Perineurium
smooth connective tissue surrounding each bundle of fibres
Epineurium
fibrous tissue surrounding and enclosing a number of bundle of nerve fibres. Most large nerves are covered by epineurium.
sensory (afferent nerves) function
carry information from the body to the spinal cord.
sensory receptors
specialised endings of sensory neurones respond to different stimili inside and outside the body
Somatic, cutaneous or common senses
originate from the skin. pain touch heat and cold
proprioreceptor senses
originate in the muscle and joints. they send information to the brain about the position of the body and it’s parts in space, enabling maintenance of posture and balance.
special senses
hight, hearing, balance, smell and taste
autonomic afferent nerves
originate in internal organs, glands and tissues e.g. the baroreceptoes involved in the control of BP. and the chemoreceptors involved in the control of respiration and are associated with reflex regulation of involuntary activity and visceral pain.
Motor / efferent nerves
originate in the brain, spinal cord and autonomic ganglia. they transmit impulses to the effector organs: muscles and glands.
what are the two types of motor nerves?
somatic nerves - involved in volunatary and reflex skeletal muscle contraction
autonomic nerves (sympathetic and parasympathetic) - involved in cardiac and smooth muscle contraction and glandular secretion, all involuntary functions.
three layers of the mininges
dura mater
arachnoid mater
pia mater
Diagram of the brains ventricles
Diagram to show structure of the brain
pons
part of a highway-like structure between the brain and the body known as the brainstem. The brainstem is made up of three sections, and carries vital information to the body. The pons relays information about motor function, sensation, eye movement, hearing, taste, and more
medulla oblongata
lays a critical role in transmitting signals between the spinal cord and the higher parts of the brain and in controlling autonomic activities, such as heartbeat and respiration
cerebellum
s important for making postural adjustments in order to maintain balance. Through its input from vestibular receptors and proprioceptors, it modulates commands to motor neurons to compensate for shifts in body position or changes in load upon muscles.
grey matter
serves to process information in the brain. The structures within the grey matter process signals from the sensory organs or from other areas of the grey matter. This tissue directs sensory stimuli to the neurons in the central nervous system where synapses induce a response to the stimuli.
white matter
the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons).
functions in affecting learning and brain functions, modulating the distribution of action potential, and coordinating communication between the different brain regions
grey matter and white matter in the spinal cord diagram
Reflex arc
a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain.
