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The Nervous System - Coggle Diagram
The Nervous System
Neurotransmitters
Small molecules that facilitate the transmission of nerve impulses between neurons in a nerve pathway.
Role: carry messages(chemically) across the synapse from one neuron to another
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The arrival of a nerve impulse(action potential) causes exocytosis and release of the neurotransmitter from the presynaptic cell into the synaptic cleft.
The neurotransmitters diffuses across the gap, binds to its specific receptors in the membrane of the post synaptic neuron and initiates a nerve impulse (action potential) to travel along the post synaptic neuron
The binding of the neurotransmitters opens protein channels and initiates a nerve impulse by allowing the diffusion of sodium and potassium ions into the postsynaptic cell.
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Reflex Response
A reflex is an automatic and involuntary repose to a stimulus that is not under the direct control of the brain.
A reflex occurs via specialised nerve pathways called reflex arc that allow organisms to response rapidly to a stimulus.
A stimulus activates sensory receptors that send nerve impulses to the spinal cord. Relay neurons in the spinal cord then transmit the impulse directly to a motor neuron which activates and effector.
A reflex is a rapid response as the nerve impulse is conducted along very few neurons and crosses very few synapse. Reflex serve a range of vital function including responding to environmental stimuli, avoiding and reducing tissue damage, maintaining balance and posture, finding food and mates
Central Nervous System
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Organised into specific regions that regulate life processes and coordinate responses to sensory stimuli
The spinal cord- conveys information to and from the brain as well generating basic patterns of movements and producing autonomic responses to stimuli
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Neurons
Specialised structure that enables the rapid transmission of nerve impulses between sensory receptors, the control centre and effectors.
Structure of neurons
Cell body
- Contains the organelles that facilitate life processes in the cell
- Contain the nucleus, cytoplasm, mitochondria, endoplasmic reticulum, ribosomes, the Golgi body and lysosomes
Dendrite
- Extensions of the cell body that receive signals from the axon terminal of other neurons. Dendrites convert these signals into berve impulses that are transmitted to the cell body
Axon
A long fibre that conducts nerve impulses from cell body to axon terminal and can vary in length in different types of neurons.
Myelin Sheath
- An insulating layer that increases the rate at which a nerve impulse is conducted along the axon.
- Schwann Cells make the myelin sheath. Nodes of Ranvier are small gaps in the myelin sheath and increase speed of transmission
Axon terminal
- Small branches from the axon that form the connection (synapses) with other neurons in the nervous system
Synapse
- Nerve impulses are electrochemical signals transmitted between nerve cells in the central and peripheral nervous system.
- A nerve impulse involves the diffusion of sodium and potassium ions across the cell membrane of the axon.
- The nerve impulse is transmitted across a small gap called the synaptic cleft between the axon terminal of one cell called the presynaptic neuron to the dendrites, cell body or axon of an adjacent cell, called the postsynaptic neuron.
- The terminal of the presynaptic and postsynaptic cell and synaptic cleft form a junction called synapse.
Type of neurons
The transmission of nerve impulses between the CNS and the PNS occur via three distinct types of neurons called sensory neurons, interneurons and motor neurons
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Interneurons: conduct impulses within the CNS. Interneurons relay impulses over short distances from sensory neurons to motor neurons
Motor neurons: Conduct impulses from the CNS to the effectors- glands, muscles or organs
Nerve pathway
Describe the pathway of nerve impulses as they travel between sensory receptor, the CNS and effectors. The most common effectors in nerve pathways are neurons, muscle cell and endocrine cells.
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Stimulus
change in the internal or external environment that is able to be detected by receptors in an organisms. E.g changes in internal body temperature, blood carbon dioxide levels, blood glucose concentration, blood pH. Changes in light levels in the external environment
Is a communication system that allows animals to sense and respond to changes in their internal and external environment.
Effectors are usually glands or muscle that bring about a response to a stimulus. Effectors may respond to nerve impulses or hormones