Neuroscience Chapter Overview

Drugs Affecting the Nervous System

• The central nervous system (CNS) is the body's master control unit, and the peripheral nervous system (PNS) is the body's link to the outside world.
• The spinal cord is a column of nerves connecting the brain to the peripheral nervous system.
• The brain stem connects the spinal cord to other parts of the brain and controls basic functions.
• The brain has three major parts: The forebrain (which includes the cerebrum), the midbrain, and the hindbrain (which includes the cerebellum).
• The cerebrum is responsible for higher-level functions. The cerebellum is involved in balance and coordination.
• The brain stem controls vital functions and connections.
• The autonomic nervous system regulates involuntary processes such as heart rate and digestion, operating automatically.
• The somatic nervous system carries sensory information to the CNS and relays motor commands to muscles, controlling voluntary movements.
• The sympathetic nervous system prepares the body for "fight or flight" responses to stress.
• The parasympathetic nervous system calms the body and helps conserve energy.

Nervous System Components

• The brain stem connects the spinal cord to other brain regions.
• Eight pairs of cervical nerves supply the head, neck, shoulders, arms and hands.
• Twelve thoracic nerves connect to parts of the upper abdomen and muscles in the back and chest.
• Five pairs of lumbar nerves supply the lower back and legs.
• Five pairs of sacral nerves and a pair of coccygeal nerves supply the buttocks, legs, and genitals.

Brain Divisions

• The brain includes the cerebrum, cerebellum, and brain stem.

• The cerebrum is divided into different lobes (frontal, temporal, parietal, and occipital).

  • The frontal lobe is responsible for problem-solving, emotions, reasoning, speaking, and voluntary motor activity.
  • The temporal lobe is involved in understanding language, behavior, memory, and hearing.
  • The parietal lobe is responsible for knowing right from left, sensation, reading, and body orientation.
  • The occipital lobe is associated with vision and color perception.

• The brain stem controls essential functions like breathing, body temperature, digestion, and sleep/wake cycles.

• The medulla oblongata, pons, and midbrain are parts of the brain stem.

• The diencephalon (includes the thalamus) is a key structure.

Cerebrospinal Fluid

• Cerebrospinal fluid (CSF) is produced in the choroid plexus of the lateral, third, and fourth ventricles.
• CSF flows from the lateral ventricle into the third ventricle and then through the cerebral aqueduct into the fourth ventricle.

Limbic System

• The limbic system involves the hypothalamus (hormones and regulatory processes), amygdala (processing emotions such as fear and aggression), and hippocampus (creating and storing memories).

Reticular Activating System (RAS)

• The RAS acts as a filter, relaying important stimuli to the brain and filtering out less important or unnecessary sensory input.
• The RAS receives input from touch, pain, and temperature receptors.

Spinal Cord

• The spinal cord is a column of nervous tissue carrying signals between the spinal nerves and the brain.
• Sensory nerve roots carry sensations to the cord's rear.
• Motor nerve roots carry signals from the cord's front to control movement.
• Meninges are membranes surrounding the spinal cord.
• Ganglia contain cell bodies of sensory nerve fibers.

Cranial Nerves

• Cranial nerves are pairs of nerves that emerge directly from the brain (CNS).
• Olfactory (I), Optic (II), Oculomotor (III), Trochlear (IV), Trigeminal (V), Abducens (VI), Facial (VII), Vestibulocochlear (VIII), Glossopharyngeal (IX), Vagus (X), Accessory (XI), and Hypoglossal (XII) nerves.

Neuron Cell Structures

• A neuron has a cell body, dendrites, an axon, axon terminals, and neurotransmitters.

Neuron Types

• Different neuron types include bipolar, unipolar, and multipolar neurons.

  • A multipolar neuron has multiple dendrites and one axon.

Myelin Sheath Formation

• Schwann cells form the myelin sheath around axons.

Neuron Parts

• The cell body/soma houses the nucleus and cytoplasm.
• Dendrites are branched projections increasing the neuron surface area and receiving information from other neurons.
• The axon is the elongated part transmitting information to effector cells.
• Effector cells (muscles, glands), respond to signals from axon terminals.
• Efferent fibers transmit impulses from the CNS.
• Afferent fibers transmit impulses to the CNS.

Motor Unit Structure

• Motor units include alpha-motor neurons and muscle fibers.

Nervous System Divisions

• Peripheral Nervous System (PNS). Autonomic Nervous System (ANS). Somatic Nervous System (SNS).
• Autonomic NS is subdivided into Sympathetic and Parasympathetic components.

Nerve Synapse

• The nerve synapse is where the axon of one neuron meets another neuron.
• Vesicles release neurotransmitters into the synaptic cleft.
• These neurotransmitters bind to receptors on the receiving neuron.

Postsynaptic Cell Responses

• A postsynaptic cell (e.g., a gland or muscle) might secrete hormones, have an action potential, or contract.

Neurotransmitter Action Termination

• Neurotransmitter action ends through enzyme inactivation, diffusion out of the cleft, or re-uptake.

Common Neurotransmitters

• Acetylcholine (ACh), norepinephrine, dopamine, GABA, serotonin, glutamate, endorphins, and histamine are common neurotransmitters.

Neurotransmitter Structures

• Adrenaline, norepinephrine, dopamine, and serotonin have specific structural characteristics.

Major Neurotransmitters

• These chemicals transmit signals between nerve cells. Understanding their function and imbalances can help treat various conditions.

Nervous Pathways

• Specific pathways, such as those for dopamine and serotonin, exist in the brain. These pathways influence cognitive and emotional functions.

Autonomic Nervous System

• The autonomic nervous system (ANS) regulates involuntary bodily functions via the sympathetic and parasympathetic systems.
• The sympathetic system is activated during stress or physical activity (“fight-or-flight”).
• The parasympathetic system regulates bodily functions during rest and relaxation (“rest-and-digest”).
• The two systems often work in opposition to maintain homeostasis.

Drugs Affecting CNS/PNS

• Various drugs impact the nervous system, working on different mechanisms.
• There are groups of drugs for specific conditions (ex. Anti-epileptic agents, Anti-psychotics etc.)

Critical Thinking and Case Study Approaches

• Analyze a nervous system component (ex. a neurotransmitter) and contemplate potential issues if it's not functioning correctly, the resulting symptoms in a patient, and needed treatments.

Critical Thinking Exercises

• For a given CNS/PNS condition, brainstorm potential interventions/treatments.