The Vertebrate Nervous System

Flashcards about the vertebrate nervous system and related topics.

What is the nervous system?

The control center for the body.

What is the central nervous system (CNS)?

Processing and control center; coordinating center for mechanical (muscles) and chemical (glands) actions.

What is the peripheral nervous system (PNS)?

Includes all parts of the nervous system except for the brain and spinal cord; relays information from the central nervous system to the body; includes both afferent and efferent nerve pathways.

What do somatic nerves control?

Controls skeletal muscles.

What do autonomic nerves control?

Controls smooth muscle, glands, cardiac muscle, and organs.

What is the sympathetic nervous system?

Prepares the body for stress; sets off the fight or flight response.

What is the parasympathetic nervous system?

Restores the body to a normal homeostatic balance; controls organs at rest.

What is the efferent system?

Motor nerves that initiate a response to the stimulus.

What is the afferent system?

Sensory nerves that relay information from the environment to the CNS for processing.

What is the sympathetic effect on the heart?

Heart rate increases.

What is the parasympathetic effect on the heart?

Heart rate decreases.

What is the sympathetic effect on digestive organs?

Peristalsis decreases.

What is the parasympathetic effect on digestive organs?

Peristalsis increases.

What is the sympathetic effect on the bronchioles (lungs)?

Bronchioles dilate, increasing breathing rate.

What is the parasympathetic effect on the bronchioles (lungs)?

Bronchioles constrict, decreasing breathing rate.

What is the sympathetic effect on the eyes?

Pupils dilate.

What is the parasympathetic effect on the eyes?

Pupils constrict.

What is the sympathetic effect on the bladder?

Sphincter constricts to hold urine.

What is the parasympathetic effect on the bladder?

Sphincter relaxes to release urine

What is the sympathetic effect on the skin?

Blood flow decreases

What is the parasympathetic effect on the skin?

Blood flow increases

What is the sympathetic effect on the liver?

Glucose releases

What is the parasympathetic effect on the liver?

Glucose stores

What is the sympathetic effect on the adrenal gland?

Adrenaline/epinephrine release.

What are neurons?

Functional unit of the nervous system; specialized cells that transmit nerve impulses.

What are glial (neuroglial) cells?

Non-conducting cells that provide nutritional and structural support to neurons.

What are sensory neurons (afferent neurons)?

Sense and relay information (stimuli) from the environment to the central nervous system; located in clusters called ganglia in the peripheral nervous system.

What are interneurons (association neurons)?

Integrate and interpret sensory information and send messages to motor neurons; located mostly in the brain and spinal cord.

What are motor neurons (efferent neurons)?

Relay information to the effectors (muscles, organs, and glands) which produce a response.

What is the structure of Sensory Neurons (Afferent Neurons)?

Usually unipolar – contain a single process connected to the cell body. Example: pressure receptors in the skin.

What is the structure of Sensory Neurons (Afferent Neurons)?

Some are bipolar – contain two processes connected to the cell body. Example: retinal receptors

What is the structure of Interneurons (Association Neurons)?

Multipolar – contain multiple processes connected to the cell body. Example: spinal cord reflex arcs

What is the structure of Motor Neurons (Efferent Neurons)?

Multipolar. Example: spinal motor neurons.

What are dendrites?

Cytoplasm extensions which are usually branched; range in numbers from one to thousands; receive signals from the environment or other neurons; transmit signals to the cell body.

What is the cell body (soma)?

Contains a large nucleus; cytoplasm contains organelles including numerous mitochondria, lysosomes, Golgi bodies, and rough endoplasmic reticulum; receives and integrates impulses from the dendrites; if there is a large enough membrane excitation, the cell body sends the collected signals as an impulse to the axon hillock; the nerve impulse will then travel from the axon hillock to the axon.

What is the axon?

Long extension of cytoplasm; carries nerve impulses to the effectors or other neurons.

What is the myelin sheath?

Made up of special glial cells called Schwann cells that form a white coat of fatty protein; acts as an insulator for the neuron and prevents the loss of ions.

What is the end brush?

Located at the end of the axon; contains the axon terminals at the end of the axon; at the end of each axon terminal is an axon terminal button, also called a synaptic knob, which connects the neuron to an effector or another neuron via the synapse.

What are the nodes of Ranvier?

Areas between the myelin sheath in which nerve impulses jump from one node to the next.

What is a reflex arc?

A neural circuit that travels through the spinal cord.

What is a reflex?

An involuntary and often unconscious reaction; occurs without brain coordination.

What is the sensory receptor component in example?

Touch a hot stove and heat receptors in the skin detect heat.

What is the sensory neuron component in example?

The nerve impulse travels to the spinal cord along afferent nerves.

What is the interneuron component in example?

The impulse is passed on to an interneuron

What is the motor neuron component in example?

The impulse is passed to a motor neuron along efferent nerves

What is the effector component in example?

The impulse from the motor neuron causes your muscles to contract, pulling your hand away

What is a monosynaptic reflex arc?

Does not involve an interneuron; there is a direct connection between the sensory neuron and the motor neuron in the spinal cord; the motor neuron is then directly connected to the effector; an example is the knee-jerk reflex.

What are nerves?

Numerous neurons held together by connective tissue; located in the peripheral nervous system.

What are Types of Neuroglia of the Central Nervous System?

Ependymal cells, Oligodendrocytes, Astrocytes, Microglia

What are Types of Neuroglia of the Peripheral Nervous System?

Satellite cells, Schwann cells

What are oligodendrocytes?

Specialized cells that wrap tightly around the axons, forming the myelin sheath in the central nervous system; speed up the electrical impulse along the axon.

What are Schwann cells?

Specialized cells that wrap tightly around the axons, forming the myelin sheath in the peripheral nervous system.

What are astrocytes?

Star-shaped glial cells that hold neurons in place (physical support) in the central nervous system; supply neurons with oxygen and nutrients; interact with neurons and synapses to assist with integrating information; release gliotransmitters by exocytosis to send signals to neurons; each astrocyte has its own specific area with no overlap with other astrocytes; the “end feet” of astrocytes also connect to blood vessels and signal them to expand or narrow, regulating the blood flow.

What are satellite cells?

Glial cells that provide the physical support to neurons in the peripheral nervous system.

What are ependymal cells?

Line the cavities of the central nervous system and make up the walls of the ventricles of the brain; create and secrete the cerebrospinal fluid; circulate cerebrospinal fluid with beating cilia.

What are microglia?

Special immune cells found only in the brain (central nervous system) that detect damaged or unhealthy neurons, and clean up brain debris; engulf foreign bacteria and viruses by phagocytosis, and display foreign antigens on the cell surface to aid in cell recognition of foreign invaders.

What are nerve impulses?

Electrochemical messages created by the movement of ions through the nerve cell membrane.

What is the sodium-potassium pump?

Moves 3 Na+ ions out of the neuron and 2 K+ ions into the neuron; the result is more K+ ions inside the neuron and more Na+ ions outside of the neuron.

What are ion channels?

Always open, allowing diffusion of ions into and out of the neuron along the concentration gradient; there are many K+ ion channels and very few Na + ion channels, meaning more Na+ ions are kept outside.

What are voltage-gated channels?

Open only when stimulated, and change the charge separation across the membrane; Na+ voltage-gated channels open in response to a stimulus; K+ voltage-gated channels open to re- establish the gradient after the nerve impulse.

Na+ and K+ conditions outside of membrane when the neuron at rest?

High Na+ and low K+.

Inside of membrane when the neuron at rest?

Low Na+ and high K+; Negatively charged proteins and large anions are also found inside.

What is resting potential?

Charge separation, or polarization, across the neural membrane.

What is the difference between the number of positive charges on the inside of the neuron relative to the outside?

-70 millivolts (mV) at the resting potential.

What is action potential?

A temporary disruption to the polarization of the neuron by the movement of ions.

What happen to initiate an action potential?

A threshold stimulus must be met; if the threshold is met (about -55 mV), the stimulus causes the voltage-gated Na+ channels to open, allowing Na+ to move into the neuron.

What is Threshold Stimulus?

A threshold must be met in order to initiate an action potential; the threshold level is about -55 mV in mammals.

What does the fact the the intensity and speed of transmission of the impulse is the same no matter how large the stimulus was, mean?

This means the neuron fires maximally whether the stimulus reaches the threshold or goes beyond it.

What happens in repolarization?

Voltage-gated Na+ channels close and voltage-gated K+ channels open, and K+ moves out of the neuron; In addition, the Na+-K+ pump continues to transport 3 Na+ ions out of the neuron and 2 K+ ions into the neuron to restore the neuron to resting potential.

What is refractory period?

The amount of time it takes for the voltage-gated Na+ channels to close again, and for the neuron to be repolarized.

What means Wave of Depolarization?

Transmission of the Nerve Impulse.

How is the depolarization?

Depolarization is propagated along the neuron, as adjacent voltage-gated Na+ channels are opened .

Why A myelinated axon has a faster action potential?

Schwann cells wrap around the axon, producing the myelin sheath which prevents the movement of ions across those myelin-covered areas, which act as an insulator.

What is Transfer to a Target Cell?

The neuron will respond with depolarization or hyperpolarization; the effector will have a response .

What is the membrane of the neuron at the end brush?

Is called the presynaptic membrane

What is the membrane of the neuron at the dendrites or the membrane of the effector that will receive the impulse?

Is called the postsynaptic membrane

The Synaptic Cleft & The Action Potential-The presynaptic and postsynaptic membranes are not in direct contact with each other ?

The space between them is called the synaptic cleft .

What happens with the neurotransmitters-The Synaptic Cleft & The Action Potential?

Chemicals called neurotransmitters are released from the presynaptic membrane and cross the synaptic cleft. At the postsynaptic membrane, neurotransmitters bind to receptors

What happens with the electric - The Synaptic Cleft & The Action Potential

Protein channels in the presynaptic membrane release ions

What happens with the Synapse (Two Neurons)?

The opening of voltage-gated calcium channels sends calcium (Ca2+) into the neuron, triggering the release of neurotransmitters from the presynaptic membrane by the exocytosis of specialized vesicles called synaptic vesicles.

What is Depolarizing - Synapse (Two Neurons)?

The uptake of the neurotransmitter by the receptors in the postsynaptic neural membrane causes voltage-gated sodium channels to open, allowing sodium (Na+) to rush into the neuron, triggering the continuation of the action potential-this is called an excitatory postsynaptic potential .

What is the order step by step with Synapse (Two Neurons)?

Action potential arrives at axon terminal, Voltage-gated Ca²+ channels open, Ca2+ enters the presynaptic neuron, Ca2+ signals to neurotransmitter vesicles, Vesicles move to the membrane and dock, Neurotransmitters released via exocytosis, Neurotransmitters bind to receptors, Signal initiated in postsynaptic cell .

What is Hyperpolarizing - Synapse (Two Neurons)?

The uptake of the neurotransmitter by the receptors in the postsynaptic neural membrane causes the membrane interior to become more negative and stabilize resting potential, by either: Voltage-gated potassium channels opening, moving K+ out of the neuron or Voltage-gated chloride channels opening, moving Cl- into the neuron-This is called an inhibitory postsynaptic potential.

What happens with Neurotransmitter Reuptake?

The neurotransmitter is reabsorbed into the presynaptic membrane through reuptake transporters.

What triggered the The Neuromuscular Junction (Neuron & Muscle)?

The opening of voltage-gated calcium channels sends calcium (Ca2+) into the neuron, triggering the release of the neurotransmitter acetylcholine.

What happens after- the Neuromuscular Junction (Neuron & Muscle)?

Acetylcholine crosses the synaptic cleft and binds to receptors in the postsynaptic muscle membrane. Voltage-gated sodium channels open, and sodium (Na+) flows into the neuron

How many Neurotransmitters are know?

There are over 60 different chemicals that act as specific neurotransmitters.

What is Neurotransmitters facts?

The effect of the neurotransmitter depends on: The type of neurotransmitter, The ion channel activated by the neurotransmitter, The location of uptake of the neurotransmitter in the body. ➢Neurotransmitter may be inhibitory or excitatory, depending on the effector or neuron it is affecting.

What are the types of Neurotransmitters?

Monoamines, Amino Acids, Neuropeptides

What is Acetylcholine?

Affects the brain, somatic nervous system, parasympathetic nervous system. Inhibitory effect on cardiac muscles. Excitatory effect on skeletal muscles. Low levels of acetylcholine have been linked to Alzheimer’s disease. High levels of acetylcholine is linked to overstimulation of skeletal muscles.

What is Norepinephrine/Noradrenalin?

Affects the sympathetic nervous system. Excitatory effect on cardiac muscles. Increases alertness and arousal.Low levels are associated with a depressed mood, fatigue, lack of focus and difficulty losing weight. High levels have been linked to sleep problems, anxiety and ADHD.

What is Dopamine?

Excitatory effect on the brain and skeletal muscles. Inhibitory effect on some parts of the brain. Elevates mood, emotions, and energy level. Increases level of motivation, focus and attention. Increases appetite. Prevents sleep. High levels of dopamine can cause schizophrenia. Low levels of dopamine can result in Parkinson’s disease.

What is Serotonin?

Inhibitory effects on the brain. Elevates mood, alertness and arousal. Balanced levels maintain thermoregulation . Appetite suppressor, decreasing hunger. Low levels of serotonin are linked to depression and other mood disorders. High levels of serotonin are associated with autism Prozac, an antidepressant, enhances the action of serotonin.

What is Glutamate?

Excitatory effect on the central nervous system and peripheral nervous system. Increases memory and learning.Low levels of glutamate result in tiredness and poor brain activity. High levels of glutamate can cause the death of neurons in the brain, and are linked to overstimulation of the brain (migraines, seizures), depression, autism and obsessive-compulsive disorder .Dysfunctional glutamate levels are associated with many neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and Tourette’s syndrome.

What is Glycine?

Inhibitory effect on the spinal cord and brain stem. Low levels of glycine are associated with inhibited cognitive functioning High levels of glycine are associated with lack of energy (lethargy) and difficulties with breathing including apnea (pauses in breathing).

What is GABA?

Inhibitory effect on the brain. Low levels of GABA cause anxiety, seizures, tremors and insomnia. High levels of GABA have a calming effect leading to sleep, but too much GABA is linked to low blood pressure and sleep issues including daytime drowsiness. Valium, a prescription drug, increases the level of GABA to alleviate anxiety.

What is ADH (Vasopression)?

Acts as a hormone in the endocrine system and a neurotransmitter in the central nervous system. Excitatory effect on the brain. Increases memory and learning.

What is Oxytocin?

Acts as a hormone in the endocrine system and a neurotransmitter in the brain. Excitatory effect on brain. Increases prosocial behaviours (love, generosity, bonding).

What is Enkephalins?

Inhibitory effect on the central nervous system. React to stress in the body and reduce level of pain.

What is Endorphins?

Inhibitory effect on the central nervous system. Increase pleasure. Reduce level of pain in the body in vigorous exercise (body’s natural painkillers). Low levels of endorphins results in body pain. High levels of endorphins keep a person on edge at all times.