Brain and Nervous System Chapter 4 Flashcards
Central Nervous System
- the comprises of the brain and the spinal cord
Peripheral Nervous System
- the first function of the PNS is to communicate information from organs to the CNS via sensory neurons
- second function is to communicate information from the CNS to the body’s organs via motor neurons
two systems of the PNS
- Automatic Nervous System
- Somatic Nervous system
two systems of the ANS
- Parasympathetic NS
- Sympathetic NS
Parasympathetic NS
- this system is what keeps the body functioning efficiently and maintains a constant internal environment (homeostasis)
- operates in calm circumstances
- dominates the Sympathetic NS in this calm state
- the PNS maintains automatic functions (Digestion, heart rate and breathing)
Sympathetic NS
- the Sympathetic NS is like an emergency system that activates when the organism perceives itself to be in an event of stress or danger
- essential in survival because it prepares the body for survival actions (flight/freeze)
results of sympathetic NS activation
- Heart rate and blood pressure increase
- Breathing rate increases
- Sugar and fat are released to provide energy
- Pupils dilate to enhance vision
- Sweat glands increase the production of perspiration to cool the body
- Digestion is slowed
Motor Nerves
• Motor neurons carry information from the CNS to the particular muscles
that an organism intends to move.
• Efferent Nerves
These nerves carry motor information outward from the CNS to the
periphery of the body
Sensory Nerves
• Sensory neurons carry information from receptors in the skin, muscles,
joints and tendons to the CNS where the information is processed.
• Afferent Nerves
• These nerves carry sensory information inward to the CNS from the
periphery of the body
Neurons
- Neurons are the primary functional units of the nervous system
- their role is to:
- receive information from other neurons
- process this information
- communicate the information to other neurons
Dendrites
- Dendrites are the branch-like structures of the neuron
- they receive information from other neurons/sensory receptors (via synapses), and deliver this information to the cell body (of the neuron)
Soma
- the soma controls the metabolism and maintenance of the cell
- it is the control centre of the cell
axon
- the axon is the nerve fibre of the neuron
- the role is to carry information away from the soma and towards other cells
- the information is carried as an electrical impulse called action potential
Neurotransmitter
- the end of each axon has terminal buttons that secrete a chemical called neurotransmitter whenever information is sent down the axon as an electrical impulse
Glial Cells
- glial cells are no part of the neuron
- glial cells surround the neuron and hold them in place. They provide nourishment and oxygen to neurons.
- They also provide insulation for neurons to increase the speed of transmission of nerve impulses through the production of myelin
- glial cells remove dead neurons
Myelin
- myelin is a fatty substance that covers the axon of the neuron and helps speed up messages passing through the axon
- it is produced in the brain and spinal cord by glial cells (myelination)
- the small gaps between myelin segments are called nodes of Ranvier. at each node, the axon is exposed and the action potential jumps from node to node at an increased speed.
- diseases that affect Myelin (Multiple Sclerosis)
Synaptic Gap
- the synaptic gap is the space between two neurons.
- the gap is where the end of the axon (terminal buttons) comes into close proximity with receptor cites on the dendrites of the post-synaptic neuron
Steps of Communication Between Neurons
- The information is passed in the form of electrical impulses through the soma along the axon
- The neurotransmitter is secreted from the terminal buttons of the presynaptic neuron to a synapse shared with the dendrites of another neuron (chemical process).
Vesicles
In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters released at the synapse.
