Units 21-24: The Nervous System and Sensory Reception Flashcards
Homeostasis
State of relative stability within the body.
Peripheral Nervous System
Nerves that carry sensory information to the CNS and from the CNS to the extremities.
Divided into the somatic system and the autonomic system.
Neurons
Basic structural and functional units of the nervous system.
Respond to chemical and physical stimuli to conduct electrochemical signals.
Glial Cells
Are the framework for the nervous tissues.
Nourish, protect, and remove waste from neurons.
10:1 ratio to number of neurons.
Nerves
Neurons are organized into tissues called nerves.
Surrounded by protective connective tissues.
Reflex Arcs
Simple connections of neurons that explain reflexive behaviors (involuntary reaction to danger before a conscious reaction).
- Sensory receptor
- Sensory neuron
- Association/Interneuron
- Motor Neuron
- Effector
Dendrites
Short, branching terminals that receive nerve impulses from other neurons or sensory receptors, and relay the impulse to the cell body.
Branching increases surface area available to receive information.
Cell Body
Of a neuron. Contains the nucleus and is the site of the cell’s metabolic reactions.
Processes input from the dendrites, relays input to the axon.
Are the signals more inhibitory or excitatory?
Axon
Conducts impulses away from the cell body. Terminal end of axon branches into fibres.
Releases chemical signals into the space between it and neighboring cells.
Myelin Sheath
A fatty layer around the axon.
Protects the axon and speeds the rate of nerve impulse transmission.
Made of Schwann cells.
Schwann Cells
A type of glial cell.
Form myelin by wrapping themselves around the axon.
Membrane Potential
The charge separation across the membrane is a form of potential energy.
Resting Membrane Potential
The potential difference across the membrane in a resting neuron.
-70mV in most neurons.
Polarization
The process of generating a resting membrane potential of -70mV.
Is achieved by charged protein molecules in the intracellular fluid which are too big to fit through the cell membrane. Also, cell membrane is impermeable to smaller negatively charged ions; chloride.
Sodium-potassium Exchange Pump
System uses ATP to transport 3 sodium ions out of the cell and 2 potassium ions into the cell.
Contributor to polarization.
Depolarization
A neural membrane is depolarized if the transmembrane potential is reduced to less than the resting potential of -70mV.
When the voltage gaged sodium channels open, causing sodium to leave the cell rapidly.
Nodes of Ranvier
Where action potentials occur in myelinated neurons.
Action Potential
The change in charge that occurs when the gates of the K+ channels close and the gates of the Na+ channels open after a wave of depolarization is triggered.
- Sodium rushes into cell. (Depolarization triggered by voltage change)
- Potassium rushes out of the cell. (Repolarization triggered by diffusion and the rush of sodium)
- Switch. Return to normal through potassium pump. Causes refractory period.
Threshold Potential
The potential difference of -55mV.
Is what makes the action potential an all or none event.
Repolarization
The movement of potassium ions out of the cell once the region of the axon hits +35mV.
This reinstates the negative charge, overshooting to -90mV, allowing all processes to return to normal.
Refractory Period
The time after an action potential, where the membrane cannot be stimulated to undergo another action potential.
Prevents impulses from going backwards.
Synapse
The connection between two neurons, or a neuron and an effector.
Neuromuscular Junction
A synapse between a motor neuron and a muscle cell.
Neurotransmitters
Chemical messengers carry neural signal from one neuron to another, or an effector.
Have either excitatory or inhibitory effects.
Acetylcholine
A neurotransmitter that crosses a neuromuscular junction.
Excites muscle cell membrane, causing depolarization and contraction of the muscle fibre.
Cholinesterase
An enzyme that breaks down acetylcholine. Allows ion channels to close and membranes to repolarize.
Somatic System
Part of the peripheral nervous system that carries sensory information to the CNS and instructions from the CNS to the skeletal muscles.
Voluntary.
Includes neurons in the: head, trunk, and limbs.
12 pairs of cranial nerves; 31 pairs of spinal nerves.
Autonomic System
Stimulate or inhibit glandular secretions and functioning of the smooth and cardiac muscles.
Involuntary.
Controlled by the hypothalamus and medulla oblongata.
Divided into two: sympathetic and parasympathetic nervous systems.
Inhibitory Effects
Receptor proteins trigger potassium channels to open. Allowing potassium ions to flow out; more negative transmembrane potential; hyperpolarization.
Prevents an action potential.
Situations That Increase The Amount of Neurotransmitter In The Synapse
- A chemical is given that mimics the effects of the neurotransmitter.
- A chemical is given that prevents the re-uptake of the neurotransmitter.
- A chemical is given that interferes with the enzyme that breaks down the neurotransmitter.
Situations That Decrease The Amount Of Neurotransmitter In The Synapse
- A chemical that blocks the receptors for the neurotransmitter is added.
- A chemical that breaks down the neurotransmitter or
- Enhances the activity of the re-uptake of the neurotransmitter.
Grey Matter
Is grey because it contains mostly cell bodies, dendrites, and short, unmyelinated axon.
Outside area of the brain, and the H-shaped core of the spinal cord.
White Matter
Contains myelinated axons that run together in tracts.
Forms the inner region of some areas of the brain, the outer area of the spinal cord!
Cerebellum
Walnut shaped structure located below and behind the cerebrum.
Unconscious coordination of posture, reflexes, and body movements.
Voluntary motor skills.
Receives information from proprioceptors, found in skeletal muscles and joints.
Medulla Oblongata
Base of the brainstem, connects to the spinal cord.
Control automatic, involuntary responses including heart rate, blood pressure, breathing, swallowing, and coughing.
Midbrain
Found above the pons and brainstem. Relays visual and auditory information between areas of the hindbrain and forebrain.
Important role in eye movement and control of skeletal muscles.
Spinal Cord
Communication link between the brain and the peripheral nervous system.
Tissues protected by cerebrospinal fluid, soft tissues, and the spinal column.
Brain
Divided into three regions, the hindbrain, the midbrain, and the forebrain.
Protected by the skull and meninges.
Hindbrain
Includes:
- cerebellum
- medulla oblongata
- pons
Meninges
Three layers of tough elastic tissue within the skull and spinal cord.
Prevent the direct circulation of blood through the cells of the brains.
Pons
Above and in front of the medulla oblongata.
Relay center between the neurons of the right and left halves of the cerebrum, the cerebellum, and the rest of the brain.
Thalamus
Base of the forebrain.
Relays and connects information to the different parts of the brain.
Between the hindbrain, and the front brain, and the sensory system except smell.
Hypothalamus
Below the thalamus.
Regulates the homeostasis through blood pressure, heart rate, body temperature.
Regulates emotions and certain aspects of behavior.
Links between the nervous system and the endocrine system. Produces and releases hormones that regulate the pituitary gland.
Cerebrum
The big part of the brain. Divided into left and right.
Blood-brain Barrier
The separation of the blood and CNS.
Supplies the brain with nutrients and oxygen,
Forebrain
Includes:
- Thalamus
- Hypothalamus
- Cerebrum
Blood-brain Barrier
The separation of the blood and CNS.
Supplies the brain with nutrients and oxygen by transport mechanisms.
Capillaries are made of tightly fused epithelial cells, are only permeable to selective; lipid-soluble substances.
Cerebrospinal Fluid
Circulates through the space within the brain and spinal cord.
Transports hormones, white blood cells, and nutrients across the blood-brain barrier.
Circulates between layers of the meninges, and acts as a shock absorber