Nerves Flashcards
What do nerve nets (Hydra) demonstrate?
Radial symmetry
Do Hydra contain a CNS
No
What cells do Hydra contain and what are their function
Ganglion cells to provide connections in many directions
What are the properties of nerve nets?
-Axons are non-myelinated
-Slow conduction speed (5m/s-1)
-Sense light and chemicals
What is the purpose of the nervous system
Detects change inside the body or in the local environment to respond appropriately.
What are the two parts of the nervous system and explanation?
- The central nervous system (CNS)- the brain and spinal cord surrounded and protected by a tough protective membrane (meninges)
- The peripheral nervous system (PNS)-comprised of somatic nervous system-nerves originating in brain or spinal cord. Includes sensory neurons and motor neurons
What is the PNS
Peripheral nervous system- unconscious control of internal organs e.g. heartbeat, digestion
What is a sensory neurone
-Carries nerve impulses from receptor cells (in sense organs) to coordinator)
-The coordinator is CNS
What is a relay neurone
-Lie in CNS
-Receive impulses from sensory neurons and send impulses to motor neurons
What is a motor neuron
Carry impulses from coordinator (CNS) to effector organs
What is an effector
Brings out the response- muscle or gland
What is a dendrite
thin extensions which carry impulses toward the cell body
What is an axon
Long cytoplasmic extensions which transmit impulses away from the cell body
What are schwann cells
Cells that surround neurones and insulate them
What is a mylein sheath
Schwann cells grow around axons to form a multi-layered fatty sheath acting as an electrical insulator that speeds up transmission along the axon
What are Nodes of Ranvier
areas along the axon where mylein sheath is missing for faster nerve impulse conduction (saltatory conduction)
What is the cell body
Parts of neurone which contain nucleus , RER, mitochondria etc.
What are axon endings
Secrete a neurotransmitter which results in depolarisation of adjacent neurone
What are reflexes
Rapid, involuntary responses to stimuli by the reception of information from receptor to effector
What is the reflex arc definition
Pathway travelled by the nerve impulses during reflex action
Where are most reflexes
spinal cord
What is the process of the reflex arc
- Stimulus
- Receptors detect stimulus- convert it to an electrochemical signal
- Sensory neurone transmits impulse to the spinal cord
4.Sensory neurones enter the spinal cord via the dorsal root.
5.The integration centre involves one synapse (mono synaptic) or two or more synapses (polysynaptic) in the grey matter of the spinal cord. - The sensory neurone synapses with a relay neurone in the grey matter of the spinal cord
7.Release of a neurotransmitter generates and action potential in the relay neurone - Repeated at the synapse between the relay and motor
- Action potential is transmitted along the motor neurone
- The motor neurone travels via the ventral root
- A motor neurone transmits a nerve impulse from spinal cord to the effector.
What is the effector in a somatic reflex
skeletal muscle
What is the effector in autonomic reflexes
smooth muscle, cardiac muscle or glands
