02 anatomy of the nervous system

How is the nervous system organized, and what are the functions of its main divisions?

Central nervous system (CNS): Consists of the brain and spinal cord. It processes information and coordinates responses.

Peripheral nervous system (PNS): Connects the CNS to the rest of the body.

Somatic nervous system: Controls voluntary movements and carries sensory information.

Autonomic nervous system: Regulates involuntary functions of internal organs.

• Sympathetic division: Prepares the body for action (“fight or flight”).

• Parasympathetic division: Supports rest and digestion.

Sensory (afferent) neurons: Carry information toward the CNS.

Motor (efferent) neurons: Carry commands away from the CNS.

Interneurons: Connect neurons and process information within the CNS.

What are the main types of nervous system cells, and what are their structures and functions?

Neurons: Specialized cells that receive, process, and transmit information.

Cell body (soma): Contains the nucleus and maintains the cell.

Dendrites: Receive incoming signals.

Axon hillock: Helps initiate action potentials.

Axon: Conducts electrical signals away from the cell body.

Synaptic terminals: Communicate with other cells at synapses.

Glial cells: Support, protect, and maintain neurons.

Astrocytes: Support neurons and contribute to the blood-brain barrier.

Microglia: Provide immune defense and remove damaged cells and debris.

Oligodendrocytes: Form myelin around axons in the CNS.

Schwann cells: Form myelin around axons in the PNS.

What are the three meninges, and how do they protect the CNS?

The meninges are three protective membranes surrounding the brain and spinal cord:

1. Dura mater: The tough, outermost layer that provides strong mechanical protection.

2. Arachnoid mater: The middle, web-like membrane. The subarachnoid space beneath it contains cerebrospinal fluid.

3. Pia mater: The delicate, innermost layer that closely follows the surface of the brain and spinal cord.

Cerebrospinal fluid (CSF):

Circulates around the brain and spinal cord and through the brain’s ventricles.

Cushions the CNS against mechanical impacts.

Provides additional protection and helps maintain the CNS environment.

→ Together, the meninges and CSF protect the brain and spinal cord from injury.

What is hydrocephalus, what causes it, and how can it affect the brain?

Hydrocephalus is an abnormal accumulation of cerebrospinal fluid (CSF) in the brain’s ventricles.

Possible causes include:

Obstruction: CSF flow is blocked.

Reduced absorption: CSF is not reabsorbed properly.

Excessive production: Too much CSF is produced.

The accumulation can enlarge the ventricles and increase pressure on surrounding brain tissue. Possible consequences include headaches, nausea, changes in vision, and neurological problems.

What is the blood-brain barrier, what does it do, and which substances can cross it?

The blood-brain barrier (BBB) is a selective barrier between the bloodstream and brain tissue.

Main function: Protects the brain by controlling which substances can enter it.

Nutrient transport: Glucose is an important energy source that can cross the BBB.

Selective permeability: Some substances can cross the barrier, while others are restricted.

Examples mentioned in the lecture: Herpes simplex virus type 1 (HSV-1), heroin, marijuana, and antidepressants are discussed in relation to crossing the BBB.

Disruption of the BBB: Can occur in conditions such as stroke, cancer, traumatic brain injury, and multiple sclerosis.

The BBB therefore helps maintain a stable environment for the brain while allowing essential substances to enter.

What are the three main brain divisions, and which structures belong to each division?

Hindbrain:

Medulla

Pons

Cerebellum

Reticular formation

Midbrain:

Superior and inferior colliculi

Periaqueductal gray

Cerebral aqueduct

Substantia nigra

Forebrain:

Thalamus

Hypothalamus

Cerebral cortex

Limbic system

What are the main structures of the hindbrain and midbrain, and what do they do?

Hindbrain:

Medulla: Controls vital autonomic functions such as breathing and heart rate.

Pons: Participates in sleep, arousal, and communication between brain regions.

Cerebellum: Coordinates movement, balance, posture, and motor learning.

Reticular formation: Involved in alertness, attention, and sleep-wake regulation.

Midbrain:

Superior colliculi: Involved in visual orienting and eye movements.

Inferior colliculi: Involved in auditory processing.

Periaqueductal gray: Participates in pain modulation and defensive responses.

Cerebral aqueduct: A channel through which CSF flows between ventricles.

Substantia nigra: Important for movement control and dopamine signaling.

What are the functions of the thalamus, hypothalamus, and four lobes of the cerebral cortex?

Thalamus:

Relays much of the sensory information going to the cerebral cortex.

Helps process and direct incoming information.

Hypothalamus:

Maintains homeostasis.

Regulates body temperature, hunger, thirst, and other basic drives.

Helps control hormonal functions through its relationship with the endocrine system.

Four lobes of the cerebral cortex:

Frontal lobe: Planning, decision-making, voluntary movement, and aspects of personality.

Parietal lobe: Processing touch and other bodily sensations, as well as spatial information.

Temporal lobe: Auditory processing, language-related functions, and memory.

Occipital lobe: Primarily responsible for visual processing.

What is the limbic system, and what are the roles of the amygdala and hippocampus?

The limbic system consists of interconnected brain structures involved particularly in emotion, motivation, and memory.

Amygdala: Plays an important role in processing emotions, especially fear, and in recognizing emotionally significant stimuli.

Hippocampus: Essential for forming new memories and for aspects of learning and spatial memory.

These structures interact with other brain regions to connect emotional experiences with learning and memory.

What is the spinal cord, how is it organized, and what are its main functions?

Location: The spinal cord is part of the central nervous system (CNS) and extends from the brainstem through the vertebral canal.

Main functions:

Communication: Carries sensory information from the body to the brain and motor commands from the brain to the body.

Reflexes: Coordinates fast, automatic responses to certain stimuli without requiring the brain to initiate the response.

Gray matter: Contains mainly neuron cell bodies, dendrites, and synapses; it is located centrally in the spinal cord.

White matter: Contains mainly myelinated axons that carry information up and down the spinal cord; it surrounds the gray matter.

Spinal nerves: Connect the spinal cord with the rest of the body and carry sensory and motor information.

Spinal cord injury: Can interrupt communication between the brain and body, potentially causing loss of sensation, impaired movement, or paralysis below the level of injury. The effects depend on the location and severity of the injury.