NS_and_Brain

Nervous System Overview

The Nervous System and The Brain

Focus: Understanding the roles and interactions within the nervous system.Objectives:

• Discuss the production and significance of cAMP and cGMP in smooth muscle cells.

• Understand Alpha and Beta responses in respiratory care and their importance.

• Define additional terms for adrenergic and cholinergic agents.

• Differentiate between adrenergic and cholinergic agents.

• Contrast nicotinic and muscarinic receptors and their organ responses.

• Differentiate between the sympathetic and parasympathetic divisions of the nervous system.

• Define tone and discuss how the sympathetic and parasympathetic systems maintain it.

• List the major divisions of the nervous system.

Major Divisions of the Nervous System

Central Nervous System (CNS)

• Comprises the brain and spinal cord.

• Functions as integrative and control centers.

Peripheral Nervous System (PNS)

• Includes cranial and spinal nerves.

• Acts as communication lines between CNS and the rest of the body.

• Divided into:

  • Sensory (afferent) division: Conducts impulses from receptors to CNS.

  • Motor (efferent) division: Conducts impulses from CNS to effectors (muscles and glands).

  • Sympathetic division: Mobilizes body systems during activity ("fight or flight").

  • Parasympathetic division: Conserves energy; manages "housekeeping" functions during rest.

Autonomic Nervous System (ANS)

• Controls involuntary functions (heart rate, respiration, sweating, digestion).

• Contains two main divisions: Sympathetic and Parasympathetic.

Sympathetic Nervous System

• Dominates in stressful situations ("fight or flight").

• Key effects:

  • Increases heart rate (↑HR) and blood pressure (↑BP).

  • Causes vasoconstriction and bronchodilation.

  • Increases respiratory rate (↑RR) and depth.

• Neurotransmitters:

  • Presynaptic: Acetylcholine (Ach) at the ganglia.

  • Postsynaptic: Norepinephrine (NE) primarily at the target organs. NE is responsible for activating adrenergic receptors throughout the body, leading to the physiological changes associated with the stress response.

• Receptors:

  • Alpha (α): Primarily responsible for vasoconstriction and increasing blood pressure.

  • Beta one (β1): Increases heart rate and force of contraction, enhancing cardiac output.

  • Beta two (β2): Primarily causes bronchodilation, facilitating increased airflow during stress responses.

Parasympathetic Nervous System

• Active during calm and restful periods ("feed and breed").

• Key effects:

  • Decreases heart rate (↓HR) and blood pressure (↓BP).

  • Causes bronchoconstriction and decreases respiratory rate (↓RR) and depth.

• Neurotransmitters:

  • Presynaptic: Acetylcholine (Ach) at the ganglia.

  • Postsynaptic: Acetylcholine (Ach) at the target organs, which binds to cholinergic receptors, leading to the activation of various organ responses focused on rest and energy conservation.

• Receptors:

  • Nicotinic (N): Located on post-synaptic neurons, facilitating transmission of signals in both parasympathetic and sympathetic pathways.

  • Muscarinic (M1, M2, M3): At effector organs and skeletal muscle; these receptors mediate effects such as decreasing heart rate and inducing bronchoconstriction.

Types of Receptors

Adrenergic Receptors (accept NE):

• Alpha (α): Vasoconstriction (↑BP).

• Beta one (β1): Increases heart rate and force of contraction.

• Beta two (β2): Bronchodilation.

Cholinergic Receptors (accept Ach):

• Nicotinic (N): Found on post-synaptic neurons.

• Muscarinic (M1, M2, M3): Decrease HR; bronchoconstriction.

Nervous System Drug Terminology

• Parasympathomimetic: Stimulates the parasympathetic nervous system.

• Parasympatholytic: Blocks effects of the parasympathetic nervous system.

• Sympathomimetic: Stimulates the sympathetic nervous system.

• Sympatholytic: Blocks effects of the sympathetic nervous system.

Inactivation of Neurotransmitters

• Acetylcholinesterase: Quick inactivation of Ach at parasympathetic terminal receptors.

• Enzymes that inactivate catecholamines:

  • COMT (catechol O-methyltransferase)

  • MAO (monoamine oxidase)