BBA Lecture 2

What are the two physical divisions of the nervous system?

The central nervous system (CNS) and peripheral nervous system (PNS).

What structures make up the central nervous system (CNS)?

The brain and spinal cord.

What are the two functional divisions of the nervous system?

The somatic nervous system and autonomic nervous system.

What does the somatic nervous system do?

It includes the sensory and motor systems.

What does the autonomic nervous system control?

Visceral organs and glands that regulate physiological functions, including heart circulation and digestion.

What are the two types of matter found in spinal cord cross-sections?

Grey matter and white matter.

What does white matter primarily contain?

Axons, neural tracts, and pathways.

What does grey matter primarily contain?

Neuron cell bodies and support cells.

What is the function of the dorsal columns of the spinal cord?

They contain the main ascending sensory tracts.

What is the function of the lateral and ventral columns of the spinal cord?

They contain the main descending motor tracts.

What is the dorsal horn of the spinal cord associated with?

Sensory information.

What is the ventral horn of the spinal cord associated with?

Motor information.

Where are the cell bodies of peripheral sensory neurons located?

In the dorsal root.

What is another name for a sensory neuron?

An afferent neuron.

What does an afferent neuron carry?

Sensory information toward the central nervous system.

What is an efferent neuron?

A neuron that carries motor information away from the central nervous system toward a target.

What are the three major divisions of the brain listed in the lecture?

The brain stem, cerebellum, and cerebrum.

What is an important role of the cerebellum in movement performance?

Controlling the timing of muscle activity.

What does the hypothalamus regulate?

Body equilibrium through endocrine regulation, as well as food, water, temperature, blood pressure, and reproduction.

What do the superior colliculi of the midbrain help control?

Orienting toward visual stimuli.

What do the inferior colliculi of the midbrain help control?

Orienting toward auditory stimuli.

What is the function of the red nucleus?

Controlling proximal upper-limb muscles.

What is the function of the pons in relation to the cerebellum?

It connects the cortex to the cerebellum through the cerebellar peduncle.

What do the vestibular nuclei help control?

Eye and postural muscles.

What are functions of the reticular nuclei?

Arousal, attention, circadian rhythm, and control of postural muscles.

What occurs at the medulla according to the lecture?

Motor and sensory decussations occur, and it contains vestibular and reticular nuclei.

What is decussation?

The crossing of nerve fibres from one side to the other.

What are the basal ganglia involved in?

Controlling movement initiation and stillness.

What is the limbic system involved in, according to the lecture?

Controlling emotion and species-typical behaviours.

What does grey matter in the cerebral cortex contain?

Neuron cell bodies and support cells.

What does white matter in the cerebrum contain?

Axons, myelin, and support cells.

What is an upper motor neuron (UMN)?

A CNS neuron with its cell body in the cortex that carries motor signals from the cortex toward the spinal cord.

What is a lower motor neuron (LMN)?

A PNS motor neuron with its cell body in the ventral horn that carries motor information from the spinal cord to a muscle.

What is another name for the lower motor neuron described in the lecture?

Alpha (α) motor neuron.

What is the main difference between upper and lower motor neurons?

Upper motor neurons carry motor commands from the cortex toward the spinal cord; lower motor neurons carry commands from the spinal cord to muscles.

Which type of motor neuron directly carries signals to skeletal muscle?

The lower motor neuron.

How do neurons communicate over long distances?

By transmitting electrical signals along their membranes.

What types of target cells can neurons communicate with?

Other neurons and non-neural cells, such as muscles, glands, and organs.

What is a presynaptic neuron?

The neuron that sends a signal to another cell.

What is a postsynaptic neuron?

The neuron that receives a signal from another cell.

Where do presynaptic neurons commonly connect with postsynaptic neurons, according to the lecture?

At the dendrites of the postsynaptic neuron.

What determines how electrical signals are generated in neurons?

How the cell membrane manages charged-ion concentrations inside and outside the cell.

What is the plasma membrane?

The two-layered lipid membrane that surrounds a neuron and controls what enters and leaves the cell.

Why is the cell membrane important for neuronal signalling?

It regulates the passage of charged ions, allowing electrical differences to develop across the membrane.

Can charged ions freely cross the cell membrane?

No. They require an opening, such as an ion channel, to cross the membrane.

What is the function of ion channels?

They selectively control which charged ions can pass through the cell membrane and when they can pass.

Do ion channels actively transport ions?

No. Ions flow through open channels according to their electrochemical gradients.

What is an electrochemical gradient?

The combined influence of differences in ion concentration and electrical charge across a membrane.

What are non-gated ion channels?

Channels that are open all the time.

What is another name for non-gated channels mentioned in the lecture?

Leakage channels.

What are gated ion channels?

Channels that open when specific conditions are met.

What are the major types of gated ion channels listed in the lecture?

Voltage-gated, mechanically gated, chemically gated, neurotransmitter-activated, calcium-gated, and ATP-gated channels.

What causes voltage-gated ion channels to open?

A change in membrane voltage.

What activates mechanically gated ion channels?

Mechanical stimulation, such as that detected by sensory receptors.

What activates chemically gated ion channels?

Chemical substances acting from outside or inside the cell.

Which two ions are especially important for the action potentials covered in this lecture?

Sodium (Na+) and potassium (K+).

What is the resting membrane potential (RMP)?

The electrical potential difference across the membrane when a neuron is at rest.

What is the resting membrane potential given in the lecture?

-70 mV.

What is the typical sodium concentration inside a neuron at rest?

Low relative to the extracellular concentration.

What is the typical sodium concentration outside a neuron at rest?

High relative to the intracellular concentration.

What is the typical potassium concentration inside a neuron at rest?

High relative to the extracellular concentration.

What is the typical potassium concentration outside a neuron at rest?

Low relative to the intracellular concentration.

How does the electrical charge inside a resting neuron compare with the outside?

The inside is relatively negative, while the outside is relatively positive.

What is membrane polarization?

A difference in electrical charge between the inside and outside of a cell.

What is depolarization?

A decrease in the difference in electrical charge across the membrane.

What is hyperpolarization?

An increase in the difference in electrical charge across the membrane, making the inside more negative relative to the outside.

What is repolarization?

The return toward the resting membrane potential after depolarization.

What is overshoot during an action potential?

The stage when the inside of the cell becomes positive relative to the outside.

What is the action-potential threshold given in the lecture?

-55 mV.

What must happen for an action potential to begin?

The membrane must depolarize to threshold, approximately -55 mV.

What is the function of the sodium-potassium ATPase pump?

It uses energy from ATP to move sodium out of the cell and potassium into the cell, maintaining their concentration gradients.

Which ion does the sodium-potassium ATPase pump move out of the cell?

Sodium (Na+).

Which ion does the sodium-potassium ATPase pump move into the cell?

Potassium (K+).

What does ATP provide to the sodium-potassium pump?

The energy required to move ions against their concentration gradients.

What is the state of voltage-gated sodium and potassium channels at rest, according to the lecture?

They are closed.

How does the sodium-potassium pump help prepare a neuron for an action potential?

It maintains sodium and potassium concentration differences that help establish the resting membrane potential.

What are the two major types of electrical signals discussed in the lecture?

Graded potentials and action potentials.

What are graded potentials?

Changes in membrane potential whose strength is proportional to the strength of the triggering event.

Where do graded potentials occur?

In the dendrites and cell body of a neuron.

What types of channels can generate graded potentials?

Mechanically gated and chemically gated channels.

What is an excitatory postsynaptic potential (EPSP)?

A graded potential that depolarizes the postsynaptic membrane.

What is an inhibitory postsynaptic potential (IPSP)?

A graded potential that hyperpolarizes the postsynaptic membrane.

What is local current flow?

The movement of electrical charge through a cell as a wave of depolarization or hyperpolarization spreads.

Where do graded potentials travel before potentially triggering an action potential?

They spread through the cell toward the axon hillock.

What happens to graded potentials as they travel through the cell?

They lose strength because charge leaks across the membrane.

What is the axon hillock's role in action-potential initiation?

It is the trigger zone where graded potentials are summed and an action potential can begin if threshold is reached.

What is summation of graded potentials?

The addition of excitatory and inhibitory inputs to determine whether the membrane reaches threshold.

What is spatial summation?

The addition of inputs arriving at different locations on a neuron at approximately the same time.

What is temporal summation?

The addition of inputs arriving close together in time.

What is the difference between spatial and temporal summation?

Spatial summation combines inputs from different locations at the same time; temporal summation combines inputs occurring close together in time.

What happens when the sum of graded potentials at the axon hillock reaches threshold?

An action potential is triggered.

What is postsynaptic integration?

The process of combining excitatory and inhibitory inputs to determine the postsynaptic neuron's response.

Approximately how many presynaptic inputs can a neuron receive, according to the lecture?

More than 10,000.

What is the difference between graded potentials and action potentials in terms of distance?

Graded potentials travel short distances, while action potentials carry signals over long distances.

What types of channels generate action potentials?

Voltage-gated ion channels.

What does all-or-none mean for an action potential?

An action potential occurs fully once threshold is reached; a subthreshold stimulus does not produce one.

Do action potentials decrease in size as they travel along the axon?

No. They remain the same size as they travel.

What happens when summed graded potentials reach approximately -55 mV?

Voltage-gated sodium channels open and an action potential begins.

What is the first major ionic event during action-potential depolarization?

Sodium ions rush into the cell through open voltage-gated sodium channels.

What causes the rapid depolarization phase of an action potential?

The influx of sodium ions through voltage-gated sodium channels.