neuronal communications Flashcards
define pacinian corpuscle
a pressure sensor found in the skin
define sensory receptors
cells/ sensory nerve endings that respond to a stimulus in the internal/ external environment of an organism and can create action potentials
define transducer
a cell that converts one form of energy into another , in this case to an electrical impulse
define motor neurone
neurones that carry an action potential from the CNS to the effector
define myelinated neurones
has an individual layer of myelin around it
define non myelinated neurones
has no individual layers of myelin
what are the different types of neurones
motor
sensory
relay
define sensory neurones
carry the action potential from a sensory receptor to the CNS
define relay neurones
connect sensory and motor neurones
each type of transducer is adapted to detect ?
changes in a particular form of energy , this may be a change in light levels , change in pressure on the skin or one of many other energy changes , other receptors detect the presence of chemicals
name the sensory receptor and energy change involved for each stimulus
- change in light sensitivity
- change in temperature
- change in skin pressure
- change in sound
- movement
- change in length of muscle
- chemicals in the air
- chemicals in food
- light sensitive cells (cones and rods) in the retina - light to electrical
- temperature receptors in the skin and the hypothalamus - heat to electrical
- pacinian corpuscles in the skin- movement to electrical
- vibration receptors in the cochlea of the year- movement to electrical
- hairs in the inner ear- movement to electrical
- muscle spindles in skeletal - movement to electrical
- olfactory cells in epithelium lining the nose- these receptors detect the presence of a chemical and create an electrical nerve impulse
- chemical receptors in taste buds on tongue - same as above
describe the structure and function of the pacinian corpuscle
is an oval shaped structure that consists of a series of concentric rings of connective tissue wrapped around the end of a nerve cell. when pressure on the skin changes this deforms the rings of connective tissue , which push against the nerve ending
the corpuscle is sensitive only to changes in pressure that deform the rings of connective tissue . therefore when the pressure is constant they stop responding
describe the structure of neurons
- many are very long so that they can transmit the action potential over a long distance
- the cell surface membrane has many gated ion channels that control the entry or exit of sodium , potassium or calcium ions
- sodium/ potassium pumps use ATP to actively transport sodium ions out of the cell and potassium ions into the cell
- neurones maintain a potential difference across their cell surface membrane
- a cell body contains the nucleus , many mitochondria and ribosomes
- numerous dendrites connect to other neurones. the dendrites carry impulses towards the cell body
- an axon carries impulses away from the cell body
- neurones are surrounded by a fatty layer that insulates the cell from electrical activity in other nerve cells nearby, this fatty layer is composed of schwann cells closely associated with the neurone
what are the differences between the different types of neurones
- motor neurones have their cell body in the CNS and have a long axon that carries the action potential out of the effector
- sensory neurones have a long dndron carrying the action potential from the sensory receptor to the cell body , which is positioned just outside the CNS . they have a short axon carrying the acyion potential into the CNS
- relay neurones connect the sensory and motor neurones together. they have many short dendrites and a short axon . the number of dendrites and the number of divisions of the axon is variable . relay neurones are an essential part of the nervous system , which conducts impulses in coordinated pathways
describe myelinated neurones
- has an individual layer of myelin around it
most sensory and motor neurones are associated with many schwann cells , which make up a fatty sheath called the myelin sheath . these schwann cells are wrapped tightly around the neurone so the sheath actually consists of several layers of membrane and thin cytoplasm from the schwann cells
at intervals of 1-3 mm along the neurone there are gaps in the myelin sheath. these are called the nodes of ranvier. each node is very short.
because the myelin sheath Is tightly wrapped around the neurone it prevents the movement of ions across the neurone membranes. therefore movement of ions across the membrane can only occur at the node of ranvier , this means that the impulse or action potential , jumps from one node to the next . this makes conduction much more rapid