The Nervous System Flashcards
what two parts is the human nervous system composed of?
the central nervous system (CNS) and the peripheral nervous system (PNS)
what is the CNS composed of?
the brain and the spinal cord
what is the PNS composed of?
nerves and ganglia (collection of nerves) on the outside of the CNS
what do the responses of external or internal stimuli involve?
the reception of information and its transfer from a receptor to an effector via the nervous system or as hormones via the blood in the endocrine system
define stimulus
a detectable change in the external or internal environment of an organism
give examples of stimulus
light
pressure
temperature
define receptor
detects stimulus (one form of energy) and converts this to electrical energy to send the information as an electrical impulse to the central nervous system via neurones
give examples of receptors
photoreceptor
thermoreceptor
mechanoreceptor
osmoreceptor
chemoreceptor
define effector
receives electrical impulses from the CNS and brings about a response
give examples of body receptors
muscles
glands
what three functional types (neurones) are in mammals that generate and transmit nerve impulses?
sensory
motor
relay (connector)
what is a sensory neurone?
it brings impulses from the sense organs or receptors into the CNS
what is a motor neurone?
carries impulses from the CNS to the effector organs (which are the muscles and glands)
what is a relay neurone?
receives impulses from certain neurones and passes them on to other appropriate neurones and it’s found within the spinal cord
where is the position of the cell body in a sensory neurone?
in the middle of the neurone
where is the position
of the cell body in the motor and relay neurone?
at the start of the neurone
what neurone out of the three is unmyelinated?
relay neurone
what is the function of the axon?
it is an extension of the cytoplasm that transmits impulses away from the cell body to the axon endings
what is the function of the dendrites?
they are many thin extensions of cytoplasm that receive impulses from other nerve cells and transmit impulses towards the cell body
what is the function of the cell body?
it contains the nucleus and groups of ribosomes in the cytoplasm (Nissl granules) that synthesise neurotransmitters
what is the synaptic end bulb
it is the swelling at the end of the axon in which neurotransmitters are stored
what do the axon endings do?
they secrete neurotransmitters by exocytosis into the synaptic cleft
what three components is only found in the peripheral nervous system?
schwann cells
myelin sheath
nodes of ranvier
what are schwann cells?
they surround peripheral neurones in vertebrates and grow around the axon to form a multi-layered myelin sheath
what is the myelin sheath?
they are formed as schwann cells grow around the axon in peripheral neurones and provide electrical insulation to speed up nerve impulse transmission
what are the nodes of Ranvier?
intervals in the myelin sheath between adjacent schwann cells
what is important to label if an exam question asked you to label a neurone and it was pointing to that structure?
the schwann cell nuclues
what is the spinal cord and what is it protected by?
it is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. most of the peripheral nerves originate from the spinal cord
protected by the spinal column
what is the function of the spinal cord?
it is the transmission of neural signals between the brain and the rest of the body and also contains neural circuits that can independently control numerous flexes
what is the spinal cord made up of?
a central area of grey matter which mainly contains nerve cell bodies and is surrounded by white matter which consists of nerve fibres surrounded by myelin sheath axons
the spinal cord is surrounded by membranes called meninges
what is meant by white matter and grey matter?
when the spinal cord is observed, the cell bodies in the grey matter absorb the dye better so it is a dark colour when looked at
the fatty tissue isn’t as water soluble so it repels the dye and leaves a white colour when observed
where are the sensory fibres and the motor fibres found in the spinal cord?
sensory fibres from the PNS enter the spinal cord on the dorsal (back) root and the cell bodies of the sensory fibres are found in the dorsal root ganglia
motor fibres leave via the ventral (front) roots
where is the central canal found in the spinal cord and what is its function?
it is a small circle in the middle of the spinal cord
it contains cerebrospinal fluid for protection