Nervous Systems

Question 1

Define Homeostasis

Answer 1

• State of relative stability within the body
• only survive within a narrow range of conditions
• E.G. Cold Extremities
• The Nervous Systems regulates body structures and processes to maintain homeostasis despite fluctuations in the internal and external environment.

Question 2

Explain why the nervous systems is critical for maintaining homeostasis.

Answer 2

The Human body must react to differences in temperatures as well as respond to various internal and external stimuli, and it must regulate these responses.

Question 3

Identify the different systems in the NS and explain the structure and function of each

Answer 3

Central Nervous System - consists of the brain and spinal cord

Peripheral Nervous System - carry sensory messages to the CNS and nerves that send information from the CNS to the muscles and glands.

Question 4

Compare the basic functions of neurons and glial cells.

Answer 4

Neurons

• the basic structural and functional units of the NS,
• they specialized to respond to physical and chemical stimuli,
• to conduct electrochemical signals,
• the to release chemicals that regulate various body processes.

Glial Cells

• outnumbered by about 10 to 1, and they account for about half of the volume of the nervous systems.
• nourish the neurons, remove their wastes, and defend against infections
• provide a supporting framework fo all the nervous-system tissue.

Question 5

List the three types of neuron, and identify their primary functions

Answer 5

1. Sensory input: Sensory neurons gather information from the snesory receptors (senses) and transmit these impulses to the central nervous system (brain and spinal cord)
2. Integration: Interneurons are found entirely within the CNS. Act as a lick between the sensory and motor neurons. Process and integrate incoming sensory information, and relay outgoing motor information.
3. Motor Output: Motor Neurons transmit information from the central nervous systems to the muscles glands, and other organs( effectors).

Question 6

Identify the basic neural pathways that is involved as you dodge a wayward tennis ball. Compare this pathways with a withdrawal reflex.

Answer 6

The eyes collect sensory information (the sight of the cat on the road,) and sensory neurons transmit this information by conducting electrochemical signals to the brain and spinal cord.

Motor neurson then carry motor output signals to the muscles (effectors), causing you to extend your foot and press the brake.

Question 7

Label its basic structures, and identify their functions

Answer 7

Dentrites - short branching terminals that receive nerve impulses from other neutrons or sensory receptors, underlay the impulse to the cell body. Receives information through the surface area

Cell Body - contains the nucleus and is the site of the cells’s metabolic reactions

Axon - which conducts impulses away from the cell body. Range to 1mm to 1m, depending on the location in the body.

Myelin Sheath - which gives the axons a glistening white appearance.

Shwann Cells - a type of glial cell, form myelin by wrapping themselves around the axon.

Question 8

Describe the structure of a myelinated neuron

Answer 8

In CNS, myelinated neurons form what is known as white matter, and unmyelinated neutrons form the grey matter. Most neutrons in the peripheral nervous system are myelinated

Question 9

Explain what the resting membrane potential is, and why it is significant to the functioning of neurons

Answer 9

The potential difference across the membrane in a resting neuron is called the resting membrane potential.

Neuron are responsible for carrying information throughout the human body. Using electrical and chemical signals, they help coordinate all of the necessary functions of life.

Question 10

Identify and explain the three factors that contribute to the resting membrane potential

Answer 10

1. The resting membrane potential provides energy for the generation of a nerve impulse in response to an appropriate stimulus.
2. Neurons become polarized as a result of several mechanisms at work at the same time. Large protein molecules that are negatively charged are present in the intracellular fluid but not outside of the cell
3. Most unstimulated neutrons is (-70 mV), and it is negative on the inside, relative to the outside.

Question 11

Explain the difference between depolarization of the neuron and an action potential.

Answer 11

• Depolarization - if transmembrane potential is reduced to less than the resting potential of (-70mV). The membrane at a node of Ranvier becomes depolarized to (-55mV), a dramatic change occurs in the membrane - called an action potential.
• Action Potential - is called an “all-or-none” event because a depolarization to between (-70mV) and (-55mV) has not effect. Any depolarization to (-55mV), or any other amount up to 0, will produce identical action potentials.

Question 12

Describe the “all-or-none” response.

Answer 12

Action Potential = “All-or-None” response depolarization to between (-70mV) and (-55mV) has no effect.

Question 13

Describe the process of depolarization in the neuron, and explain its importance in the transmission of a neural impulse.

Answer 13

The membrane is depolarized - that is, returned to its previous polarization. In the fact, the membrane potential overshoots to nearly (-90mV).

The transmission of a nerve impulse along a neuron from one end to the other occurs as a result of electrical changes across the membrane of the neuron. The membrane of an unstimulated neuron is polarized - that is, there is a difference in electrical charge between the outside. and inside of the membrane.

Question 14

Summarize the events that occur as an impulse is propagated along the length of the neuron.

Answer 14

Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential. Synapses are junctions between neurons and between neutrons and receptor or effector cells. When presynaptic neutrons are depolarized they release a neurotransmitter in to the synapse.

Question 15

Summarize the events involved in impulse transmission from the presynaptic neuron to the postsynaptic neuron

Answer 15

1. Arrival of action potential at axon terminal
2. Depolarisation of pre-synaptic membrane.
3. Synaptic versicle fuses with pre-synaptic membrane, neurotransmitter release into synaptic cleft.
4. Neurotransmitter bind to the receptor on post synaptic membrane.
5. Opening of specific ion channels allows the entry of ions, a new action potential is generated in the post-synaptic neuron.

Question 16

Identify the function of neurotransmitters in the nervous system.

Answer 16

Neurotransmitters are chemical messengers that your body can’t function without. Their job is carry chemicals signals (“messages”) from one neuron (“nerve cell”) to the target cell.

Question 17

Compare the excitatory and inhibitory effects of neurotransmitters on the postsynaptic membrane.

Answer 17

1. Excitatory neurotransmitters have excitatory effects on the neuron. The means they increase the likelihood that the neuron will fire an action potential.
2. Inhibitory neurotransmitters have inhibitory effects on the neuron. This means they decrease the likelihood that the neuron will fire an action.

Question 18

Compare and relate the functions of acetylcholine and cholinesterase.

Answer 18

1. Acetylcholine - a neurotransmitter that crosses a neuromuscular junctions.

• Acetylcholine excites the muscle cell membrane, causing depolarization and contraction of the muscle fibre.
• Acetylcholine remained in the synapse. The muscle fibre cell could not repolarize and would remain in a state of excitation.

2. Cholinesterase is released into a synapse, where it breaks down acetylcholine.

• One of the fastest acting enzymes.
• Its breaks down acetylcholine to that it can be removed from the protein receptors, thus allowing the ion channels in a fraction of a second. \
• A nerve gas called sarin destroys this functions by blocking the release of cholinesterase into the neuromuscular junctions.
• The build-up of acetylcholine, critical muscles, such as the heart and diaphragm enter a state of constant contraction or paralysis.
• Some insecticides affect insects in the same way and kill them.

Question 19

Identify the main structures of the central nervous system, and describe its general functions.

Answer 19

The CNS is the structural and functional centre for the entire nervous system.

1. The spinal cord: column of nerve tissue that extends out of the skull from the brain, and downward through a canal within the backbone.

• vital communication link between the brain and the peripheral nervous system.
• sensory nerves carry messages from the body to the effectors.
• Also the primary reflex centre, coordinating rapidly incoming and outgoing neural information.
• White matter - consists of myelinated nerve fibres
• Grey matter - unmyelinated neutrons like the cell bodies and dendrites of many spinal

2. The brain : role in maintaining homeostasis and have identified the brain as the centre for intelligence, consciousness, and the emotion.

• Brain is fragile and has a elating- like consistency.
• The skull, however from protective boy armour around the brain.
• Meninges - three layers of tough, elastic within the skull and spinal column, directly enclose the brain and spinal cord.

Question 20

Explain how the blood-brain barrier and the cerebrospinal fluid protect and the brain and spinal cord.

Answer 20

Blood-Brain Barrier: the meninges protect the central nervous systems by preventing the direct circulation of blood through the cell of the brain and spinal cord.

• Use 20% of the body’s O2 and energy supplies. the O2 supply to the brain is disrupted for even a few minutes, massive damage can occur in the brain.
• both protect the brain and supplies the brain with nutrients and O2.

Cerebrospinal Fluid : Circulating through the spaces or ventricles, within the Brin and spinal cord is the cerebrospinal fluid.

• 150mL at any one time.
• Fluid replaces about 4x each day, total amount of the fluid produced each day about 500mL.
• transports hormones white blood cells, and nutrients across. the blood-brain barrier for cells of the brain and spinal cord.
• Circulates between the two layers the meninges, the arachnoid and Pia matter, and therefore acts as a shock absorber to cushion the brain.

Question 21

Identify five homeostatic functions of the brain.

Answer 21

1. maintaining daily physiological cycles,
2. such as the sleep-wake cycle.
3. controlling appetite.
4. regulating body temperature.
5. controlling the production and release of hormones.

Question 22

Identify the major structures in the hindbrain, midbrain, and forebrain, and the functions of the structures.

Answer 22

Question 23

Identify the four lobes of the cerebrum and describe the function of each.

Answer 23

Question 24

Describe the primary areas of the brain that are responsible for the fine motor control of the muscles, as well as the area that processes sensory information from the skin.

Answer 24

The cerebellum is located behind the brain stem. While the frontal Lobe controls movement, the cerebellum, “fine-tunes” this movements. This area of the brain is responsible for fine motor movement balance, and the brain’s ability to determine limb position.

The parietal lobe is separated from the occipital lobe by the parieto-occipital sulcus and is behind the central sulcus. It is responsible for processing sensory information and contains the somatosensory cortex.

Question 25

Compare the locations and functions of Broca’s area and Wernicke’s area in the brain.

Answer 25

1. Broca’s area

• coordinates the muscles for speaking and translates through into speech.
• Damage to this area results in an inability to speak
• Affect the understanding of language

2. Wernicke’s area

• stores the information involved in language comprehension.
• Ability to utter words is not affected if this are is damaged, but the words make little sense

Question 26

Describe how early researchers studied brain structure and functions

Answer 26

Scientists first learned about brain functions by studying the brains of people with brain injuries or diseases.

For Example: injured soldiers would sometimes have damaged to certain areas of the brain, but still survive and think the injured area of the brain to loss. of function in other areas of the body

Question 27

Compare the technologies of MRI and PET for studying the brain.

Answer 27

• PET scan can be sued to diagnose conditions such as a stroke or Alzheimer’s disease, in which the deterioration of the brain leads to memory loss and confusion, and eventually lack of conscious movement.
• MRI can produce very clear and detailed images of brain structures. A giant magnet surround the person’s head, and changes in the direction of the magnetic field induce hydrogen atoms in the brain to emit radio signals. MRI can used for detected translated and displayed structural or functional image. They can searched the brain disorders, like brain tumours.

Question 28

What are the major structures involved in the somatic system?

Answer 28

The sensory-somatic nervous system consists of the cranial and spinal nerves.

• Under voluntary control, and it’s neuron service the head, trunk, and limbs
• from the receptors in the skin, tendons, and skeletal muscles.
• Carry information to the skeletal muscles.

Question 29

What role does the somatic system play in the functioning of the body?

Answer 29

The primary function of the somatic nervous system is to connect the CNS to the body’s muscles to control voluntary movements and reface arcs.

Question 30

What type of motor neurone are involved in the autonomic nervous system?

Answer 30

Visceral efferent neurons- motor neurons whose job it is to conduct impulses to cardiac muscle, smooth muscles and glands. They may originate in the brain or spinal cord (CNS). Two visceral efferent neurons are required to conduct an impulse from the brain or spinal cord to the target tissue.

Question 31

What generally triggers the sympathetic nervous system, and what are its effects on the body?

Answer 31

The sympathetic nervous system directs the body’s rapid involuntary response to dangerous or stressful situations. A flash flood of hormones boosts the body’s alertness and heart rate, sending extra blood to the muscles.

Question 32

What are generally triggers the parasympathetic nervous system, and what are its effect on the body?

Answer 32

The parasympathetic nervous system is responsible for the body’s rest and digestion response when the body is relaxed, resting, or feeding. It basically undoes the work of sympathetic division after a stressful situation. The parasympathetic nervous system decreases respiration and heart rate and increases digestion.w