5.1.3 Neuronal communication Flashcards
Why is communication needed?
-so that organisms can respond to changes in their environment to increase chances of survival
-can be in response to internal or external environment
Homeostasis
-coordinating the functions of organs in order to maintain a relatively constant internal environment
Cell signalling
-occurs through one cell releasing a chemical which has an effect on a target cell
-cells can transfer signals locally i.e neurotransmitters across synapses or across large distances i.e secretion of hormones
What is the nervous system?
-made up of the brain and spinal cord(CNS) and the neurones that connect CNS to the rest of the body(PNS)
-responsible for detecting stimuli and coordinating a response–} faster and more targeted than hormonal communication
Neurones
-specialised network of nerve cells that can transmit electrical impulses rapidly around the body so the organism can respond to internal/external changes
What are the 3 main types of neurones?
-sensory neurones= transmit nerve impulses from receptors to CNS
-relay neurones= transmit nerve impulses from sensory to motor
-motor neurones= transmit nerve impulses from CNS to effectors
Describe the general structure of a neuron
-cell body= contains nucleus, has some ER and mitochondria within cytoplasm(involved in production of neurotransmitters)
-dendrites=transmit electrical impulses towards cell body
-axons=transmit impulses away from cell body
-axon terminal=end of an axon where neuro transmitters are released
-myelin sheath=layers of plasma membrane produced by Schwann cells, act as an insulating layer to speed up electrical impulse, can also provide nutritional support(phospholipids)
-Nodes of Ranvier=gaps in the myelin sheath that speeds up transmission because electrical impulses must jump from one node to the next
Structure of a sensory neuron
-one long dendron to carry nerve impulses from receptor cells to cell body
-one short axon that carries nerve impulses from cell body to CNS
-cell body in the middle
-dendrites are not connected to cell body
Structure of a motor neuron
-many short dendrites that carry nerve impulses from CNS to cell body
-one long axon to carry nerve impulses from cell body to effector cells
-dendrites are connected to cell body
-cell body at the top
Structure of a relay neuron
-many short dendrites that carry nerve impulses from sensory neurons to cell body
-many short axons to carry nerve impulses from cell body to motor neurones
-no myelin sheath
-cell body in the middle
Describe the pathway of nervous communication
-stimulus is detected by a receptor
-electrical impulse passes from receptor to CNS via sensory neurone
-impulse is passed from sensory to motor neurone via the relay neurone in the CNS
-the motor neurone passes along electrical impulse from CNS to effectors(muscles/glands)
-effectors coordinate a response
What are sensory receptors?
-specialised cells that detect changes in the environment
-convert the stimulus they detect into a nerve impulse–} info is passed through the nervous system where a response is coordinated
What are the 2 main features of a sensory receptor?
-it is specific to a single type of stimulus
-act as a transducer= convert a stimulus into a nerve impulse called a generator potential
4 types of sensory receptors
-thermoreceptors= respond to heat in the end bulbs of Krause in the tongue
-chemoreceptors= respond to chemicals in the olfactory receptor of the nose
-photoreceptors= respond to light the cone cells of the eye
-mechanoreceptors= respond to pressure in the Pacinian corpuscle in the skin
What is the resting potential?
-the potential difference* across a neurone’s membrane when it is at rest
*the difference in charge between the inside and outside of a cell
