Nervous System part 3

What are the three main functions of the nervous system?

Sensory input, integration/processing, and motor output.

What are the two main cell types in the nervous system?

Neurons and neuroglia.

Describe the structure of a neuron.

A neuron consists of a cell body, dendrites, and an axon.

What is the role of dendrites?

To receive signals and conduct impulses toward the cell body.

What is the function of the axon?

To transmit impulses away from the cell body.

What is the function of the myelin sheath?

It insulates the axon, speeding up the transmission of nerve impulses.

What are nodes of Ranvier?

Gaps in the myelin sheath that facilitate rapid impulse conduction through saltatory conduction.

List the types of neuroglia in the CNS.

Astrocytes, oligodendrocytes, microglia, and ependymal cells.

What is the primary function of astrocytes?

To provide structural support, regulate nutrients, and maintain the blood-brain barrier.

Describe the function of Schwann cells in the PNS.

They produce the myelin sheath around peripheral axons.

What is the resting membrane potential of a neuron?

Approximately -70 mV, with the inside of the neuron more negative than the outside.

Define depolarization.

The process by which the inside of a neuron becomes less negative, initiating an action potential.

What is an action potential?

A rapid change in membrane potential that propagates along the neuron.

What occurs during repolarization?

The membrane potential returns to a negative value after an action potential.

What is the 'all-or-none' principle?

An action potential occurs fully if the threshold is reached; otherwise, it does not occur at all.

What is a synapse?

The junction between two neurons where neurotransmitters transmit signals.

Name an excitatory neurotransmitter and its role.

Glutamate; it increases the likelihood of an action potential in the postsynaptic neuron.

What is the role of GABA as a neurotransmitter?

It is inhibitory, decreasing the likelihood of an action potential.

How is neurotransmitter action stopped?

Through reuptake or enzymatic breakdown to prevent continuous stimulation.

What are the two main divisions of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS).

What does the CNS include?

The brain and spinal cord.

Describe the PNS and its components.

It consists of cranial and spinal nerves that connect the CNS to the body, including sensory and motor divisions.

How many segments does the spinal cord have?

31 segments, each with a pair of spinal nerves.

Name the primary functions of the spinal cord.

To transmit impulses to and from the brain and house spinal reflexes.

What are the three layers of the meninges?

Dura mater, arachnoid mater, and pia mater.

What is the role of the dura mater?

It is the tough outer layer, containing blood vessels and forming a sheath around the spinal cord.

What are the four lobes of the cerebrum?

Frontal, parietal, temporal, and occipital lobes.

What is the function of the cerebrum?

Responsible for sensory processing, motor control, and higher mental functions like reasoning and memory.

What is the cerebral cortex?

The outer layer of gray matter involved in processing and containing neuron cell bodies.

What are the three parts of the brainstem?

Midbrain, pons, and medulla oblongata.

Describe the function of the medulla oblongata.

It regulates vital functions like heart rate, blood pressure, and breathing.

How many cranial nerves are there?

Twelve pairs.

What is the function of the optic nerve (Cranial Nerve II)?

Vision.

What does the vagus nerve (Cranial Nerve X) control?

It controls muscles related to speech, heart rate, and digestion.

What is a reflex arc?

The pathway of a reflex, involving a sensory neuron, interneuron, and motor neuron.

Give an example of a simple reflex.

The patellar (knee-jerk) reflex.

What are the brain ventricles?

Connected cavities filled with CSF, providing protection and nutrients to the CNS.

Where is cerebrospinal fluid (CSF) produced?

In the choroid plexuses of the ventricles.

What is the function of CSF?

It cushions the brain and spinal cord and transports nutrients and wastes.

What is the primary role of the limbic system?

To control emotional responses and behavior related to survival.

Name a key structure in the limbic system associated with emotion.

The amygdala.

What is the function of the thalamus?

To relay sensory information to the cerebral cortex.

How does the hypothalamus maintain homeostasis?

By regulating functions like body temperature, hunger, and endocrine activity.

What are the two divisions of the autonomic nervous system?

Sympathetic (fight or flight) and parasympathetic (rest and digest).

Which neurotransmitter is mainly associated with the sympathetic division?

Norepinephrine.

Which neurotransmitter is mainly associated with the parasympathetic division?

Acetylcholine.

Describe the effects of the sympathetic nervous system on the heart and lungs.

Increases heart rate and dilates bronchioles.

Describe the effects of the parasympathetic nervous system on digestion.

Increases digestive activities, such as peristalsis and glandular secretion.

What is a nerve plexus?

A network of intersecting nerves that control muscles and skin of specific body regions.

Name the three main nerve plexuses.

Cervical, brachial, and lumbosacral plexuses.

What does the phrenic nerve control, and which plexus is it part of?

It controls the diaphragm and is part of the cervical plexus.

Where do sympathetic fibers originate?

From the thoracic and lumbar regions of the spinal cord (T1-L2).

Where do parasympathetic fibers originate?

From the brainstem and sacral spinal cord.

What are autonomic ganglia?

Structures where preganglionic neurons synapse with postganglionic neurons.