The Nervous System, Endocrine System, and Senses Flashcards
Central Nervous System:
Including the brain and the spinal cord. It is the coordinating center for incoming/outgoing information.
Peripheral Nervous System
Consists of nerves. Carries information between organs and CNS.
Glial Cells (Neuroglial Cells):
Structural support and metabolism of nerve cells, help with the repair.
Neurons:
The functional unit of the nervous system.
Dendrites:
Receives information from the environment or from other neurons. Conducts nerve impulses towards the cell body.
Axon:
Extension of the cytoplasm. Conducts nerve impulses away from the cell body and towards neurons or effectors. Only one axon per neuron but may form multiple branches. Very thin.
Myelin Sheath:
Fatty protein that covers most neurons. Acts as insulation and is formed by special glial cells called Schwann Cells, in the PNS. They speed up nerve impulses. Found in all PNS neurons and some CNS neurons.
Nodes of Ranvier:
Areas between sections of Myelin sheath. Help speed up nerve impulses through chemical transportation between the gaps.
Neurilemma:
A thin outer membrane that supports the axon and promotes regeneration of the damaged axon. Formed by Schwann cells. Found only in PNS nerve cells.
White Matter:
Nerves that contain myelin sheath.
Grey Matter:
Nerves that lack the myelin sheath.
The Three Types of Neurons:
Sensory neurons, interneurons, and motor neurons.
Sensory Neurons:
Receives information from sensory receptors and relays to the CNS. Has cell bodies located in clusters called ganglia outside the spinal cord.
Interneurons:
Does not have a myelin sheath. Links neurons to other neurons. Found only in the brain and spinal cord. Integrates and interprets sensory information and connects sensory neurons to motor neurons.
Motor Neurons:
Relays information to effectors.
Effectors:
Muscle/cell/organ/gland that responds to stimulus.
The Reflex Arc:
The simplest nerve pathway. Unconsciously, protects the body quickly although secondary signals are sent to the brain, the primary response is hard-wired through the spinal cord.
What does the Reflex Arc involve?
Sensory receptors, sensory neurons, interneurons, motor neurons, and effectors.
Electrochemical Impulses:
Nerve impulses created by the movement of cations through the nerve cell membrane, including sodium and potassium.
Resting Potential:
The voltage difference across a nerve cell membrane at rest. Due to a sodium-potassium pump.
Sodium-Potassium Pump:
For every 3Na+ pumped outside, 2K+ are pumped inside.
Outside a resting cell there is more ___.
Na+
Inside a resting cell, there is more ___.
K+
What is the resting potential of a cell?
-70mV.
Because of it’s negative resting potential, the membrane is said to be _________.
polarized
What three factors are polarization due to?
The outward diffusion of potassium ions, the sodium pump is more efficient than the potassium pump, and the presence of negatively charged ions stuck inside the neuron.
How is an electrochemical impulse created?
A stimulus will alter the resting potential by causing sodium to leak back into the neuron. If the stimulus is strong enough to bring the inside to ~-55mV the threshold has been met. The sodium channels immediately open wide and the K+ channels close.
Action Potential:
The voltage difference across a nerve cell membrane when the nerve is excited. The rapid influx of sodium flowing in causes a momentary reversal in polarity and shoots to 40mV. This spike induces the collapse of the resting potential in the adjacent area of the neuron.
Depolarization:
Diffusion of sodium ions into the nerve resulting in a charge reversal. Na+ gate open, K+ gate closed.
Repolarization:
Process of restoring the original polarity of the nerve ending. Na+ gate closes, K+ gate opens the flow outwards.
Hyperpolarization:
Condition in which the inside of the nerve cell membrane has a greater negative charge than the resting membrane; caused by excessive diffusion of potassium ions out the cell.
Refractory Period:
The amount of time it takes to repolarize. ~ 1 ms. During this time, the axon cannot transmit an action potential.
Neurons and impulse transmission follow the ___________ principle. This means…
all-or-none, a stimulus above the threshold, whether weak or strong, produces the same strength of signal transmission.
If something is more painful, how will this affect an impulse?
More of an impulse will be generated, but it is not a stronger impulse.
An impulse (does/doesn’t) diminish in strength as it travels along a neuron.
doesn’t
Where are sodium and potassium pumps and channels active?
At each node of Ranvier.
Saltatory Conduction:
The generation of action potential only at the node of Ranvier in myelinated axons.
Synapse:
The junction between adjacent neurons in a nerve fibre that do not actually touch end to end.
Synaptic Cleft:
The small space in between the terminal axon of the first neuron and the dendrite of the next.
Presynaptic neuron:
The neuron that carries impulses to the synapse.
Postsynaptic neuron:
The neuron that carries the impulses away.
What does a synaptic knob have/secrete?
It has vesicles that produce and secrete neurotransmitters.
How are neurotransmitter chemical messages released?
The presynaptic neuron binds to receptors on the postsynaptic neurons.
Inhibitory neurotransmitters:
Cause post-synaptic potassium channels to open fully. Pottasium will diffuse out, resting potential becomes more negative, and the neuron is hyper-polarized.
How do impulses get from one neuron to the next?
When the impulse reaches the synaptic knob, the membrane around the knob becomes permeable to calcium. Calcium causes the vesicles to fuse to the membrane of the knob and empty the neurotransmitters into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and land on receptor sites on the post-synaptic dendrite.
What happens once neurotransmitters reach the post-synaptic dendrite?
They have an excitatory post-synaptic potential which excites the post-synaptic neuron. Sodium channels on the post-synaptic dendrites open and depolarize. The action potential is achieved, and a depolarization wave spreads across the post-synaptic neuron.
What is the most common neurotransmitter? What does it do?
Acetylcholine. This neurotransmitter has an excitatory effect. It is released from the presynaptic axon, diffuses through the synapse, and lands on receptors on postsynaptic dendrites, thereby depolarizing the postsynaptic neuron.
What is the issue with acetylcholine? How can this problem be resolved?
If acetylcholine remains in the receptor sight, the sodium channels will remain open, which leads to repeated muscle stimulation. To solve this, cholinesterase breaks down the acetylcholine, and once the sodium channels close, the neuron can begin recovery. However, nerve gas deactivates cholinesterase.
Summation:
When neurotransmitters of acetylcholine from multiple pre-synaptic knobs are needed to induce action potential.
Multiple Sclerosis:
Deterioration of the myelin sheath, scar tissue on the axon, no impulse transmission, and impaired neural function.
Nerve damage due to injury:
If damaged neurons are covered by the thin membrane called neurilemma, regeneration is likely. If there is no neurilemma, there is no chance of regeneration.
Parkinson’s Disease:
Involuntary muscle contractions, insufficient production of dopamine.
Alzheimer’s disease:
Loss of memory, decreased production of acetylcholine.
List steps 1 through 7 of the events of synaptic transmission:
- The impulse reaches the synapse from the axon. Calcium channels open, and calcium ions diffuse into the pre-synaptic neurons.
- Calcium influx stimulates synaptic vesicles to move to the presynaptic membrane.
- Synaptic vesicles dump neurotransmitter substances into the synaptic cleft.
- The neurotransmitter substance diffuses across the cleft.
- The neurotransmitter substance fits into receptor sites on the postsynaptic membrane.
- An action potential is stimulated at the postsynaptic membrane, and an impulse travels down the dendrite.
- An enzyme destroys the neurotransmitter substance and clears out the synaptic cleft.
What protects the CNS?
The skull and vertebrae, the meninges, and cerebral fluid.
Cerebral fluid:
Circulates between the innermost and middle meninges of the brain. It also goes through the central canal of the spinal cord. It acts as a shock absorber and a transport medium of nutrients to the brain and waste to the blood.
The spinal cord carries _______ _______ from receptors to the brain.
sensory neurons
The spinal cord carries _____ _______ from the brain to the effector.
motor neurons
Does the spinal cord have white matter, grey matter, or both?
Both.
Dorsal roots:
Brings sensory information into the spinal cord.
Ventral roots:
Carries motor information from the spinal cord to effectors.
The brain is divided into three regions:
Forebrain, midbrain, and hindbrain.
What is the forebrain composed of?
The thalamus, hypothalamus, and cerebrum.
Thalamus:
Relays incoming information to the cerebrum. It sorts out information.
Hypothalamus:
Maintains the body’s internal equilibrium, regulates body temperature, water content, blood pressure, hunger and thirst, sex drive, mating behaviours, fight or flight response, and connects the pituitary gland in the endocrine system.
Homeostasis:
The body’s internal equilibrium.
Cerebrum:
Made of the cerebral cortex which is grey matter. It has folds called fissures to allow for more neurons. Divided into left and right hemispheres.
The right hemisphere of the cerebrum:
Visual patterns/spatial awareness and creative thought.
The left hemisphere of the cerebrum:
Verbal skills and logical thought.
Corpus callosum:
A bundle of nerves which allows the left and right hemispheres of the cerebrum to communicate.
What can cerebrum hemispheres be further divided into?
The frontal lobe, temporal lobe, parietal lobe, and occipital lobe.
Frontal lobe:
Motor control of voluntary muscles, intellectual activities, and personality.
Temporal lobe:
Vision but mostly hearing, memory, and interpretation of sensory information.
Parietal lobe:
Sensory, touch and temperature awareness, emotions, interpreting speech.
Occipital lobe:
Vision, interpreting visual information.
Midbrain:
Located below the thalamus, four spheres of grey matter, relay center for ear and eye reflexes.
Hindbrain:
Joins with the spinal cord, and contains the cerebellum, pons, and medulla oblongata.
Cerebellum:
The largest section of the hindbrain, controls limb movement, balance, muscle tone, and fine motor control.
Pons:
Passes information between the cerebellum and the medulla.
Medulla Oblongata:
Connects the CNS with PNS, controls involuntary muscle movements like breathing, swallowing, and heart rate, the coordinating center for the autonomic nervous system, motor axons cross from the mid and forebrain from one side of the CNS to the other side.
