Flashcards in The Nervous System Deck (11):
What are the parts of the nervous system ?
The central nervous system consists of the brain and the spinal cord
The Peripheral Nervous System consists of nerves that carry impulses from th CNS
What are neurons?
"A neuron is a nerve cell"
A "Sensory Neuron" carries impulses from the receptors in sense organs to the CNS
A "motor neuron" carries impulses away from the CNS to muscles and glands
An " interneuron" carries impulses within the CNS (ie.from sensory to motor neurons)
What's the function of different parts of the neuron?
Dendrites - receive information and carry electrical impulses swords the cell body
Axons - carry impulses away from th well body
Cell body - contains a nucleus and forms dendrites and axons
Myelin(sheath) - fat rich material that insulates the electrical impulses
Schwann cells - form the myelin (sheath)
Neurotransmitter swellings - Produce neurotransmitter chemicals
What are the features of nerve impulses?
An impulse travels along a neuron in the form of an electrical impulses
In order for the electrical impulses to travel it is necessary for ions to move in and out of dendrites and axons
The movement of these ions requires energy in the form of ATP
" The threshold is the least possible stimulus needed to send an impulse"
An impulse will pass along a neuron if it receives a stimulus of sufficient strength
If the stimulus is below the threshold it will fail to cause an impulse to pass
What is a synapse ?
"A synapse is the region where two neurons come into close contact, a synaptic cleft is the gap between two neurons"
Events at synapse:
- When an electrical impulse arrives at a synapse it stimulates the release of neurotransmitter chemicals(made and stored in neurotransmitter swellings). These swelling are found only at one side of the synapse (I.e they are on the sensory neuron)
- A lot of neurotransmitter chemicals made by the nervous system, ach dopamine - These chemicals diffuse across the synaptic cleft
- When the chemicals enter the motor neuron they are broken down by enzymes to generate an electrical impulse
Function of synapse
- controls the direction of impulses
What is the central nervous system?
Consists of the the brain and the spinal cord
Enclosed by three membranes called the meninges
Protective fluid called cerebrospinal fluid is located between the inner two meninges
- it controls voluntary movement receives impulses from sense organs, intelligence, personality
- divided into two cerebral hemispheres connected by corpus callosum
Left controls right hand side of the body + maths, logic
Right controls left side of body + music, shapes, emotions
- controls balance and muscle co ordination
- controls involuntary muscles e.g. intercostal muscles, the diaphragm and intestinal muscles
Thalamus and hypothalamus
- Thalamus is the sorting centre of the brain, incoming impulses at directed to correct part of brain
- hypothalamus controls internal environment of the body (homeostasis), regulates hunger + thirst+ temperature +blood pressure
The spinal cord
Carries impulses to and from the brain
Also involved in reflex actions
Parts and their functions
Meninges - surround and control the entry of materials into the brain and spinal cord
Spinal nerves - carry impulses to and from the spinal cord
Dorsal root - carries impulses into spinal cord along sensory neurons
Ganglion - swelling that contains the cell bodies of sensory neurons
White matter - contains axons
Grey matter - contains cell bodies
Central canal - contains fluid called cerebrospinal fluid
Ventral root - carries impulses out of the spinal cord along motor neurons
What is a reflex ?
"A reflex action is an automatic unconcios or involuntary response to a stimulus"
Examples: - knee jerk, blinking for protection
The benefit of reflex actions is that they allow faster responses than normal
They protect the body from harm
What's the path of a reflex action ?
1.Receptors in the finger detect the hot object
2. An impulse travels along a sensory neuron to the spinal cord
3. The impulse travels into the spine through the dorsal root
4. In the spinal cord the impulse splits
a) crosses a synapse into an interneuron
b) crosses another synapse and passes up to brain
5. From interneuron it crosses another synapse and travels out of the central root along a motor neuron