Study Notes: The Nervous System, Endocrine System, and Blood

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Chapter 7: The Nervous System

Divisions of the Nervous System

The nervous system is divided into two main parts, each with specific organs and functions. Understanding these divisions is essential for grasping how the body processes and responds to information.

Central Nervous System (CNS): Consists of the brain and spinal cord. It is responsible for integrating sensory information and coordinating body responses.
Peripheral Nervous System (PNS): Includes all neural tissue outside the CNS, such as cranial nerves and spinal nerves. It connects the CNS to limbs and organs.
Somatic Nervous System: Controls voluntary movements by innervating skeletal muscles.
Autonomic Nervous System (ANS): Regulates involuntary functions (e.g., heart rate, digestion). Subdivided into:
- Sympathetic Division: Prepares the body for 'fight or flight' responses.
- Parasympathetic Division: Promotes 'rest and digest' activities.

Major Functions of the Nervous System

The nervous system performs three primary functions:

Sensory Input: Detects changes inside and outside the body using receptors.
Integration: Processes and interprets sensory input, deciding what action is needed.
Motor Output: Activates effector organs (muscles and glands) to cause a response.

Neuroglia vs. Neurons

Neurons: Specialized cells that transmit electrical impulses. They are excitable and have a unique structure for communication.
Neuroglia (Glial Cells): Support, protect, and nourish neurons. They do not conduct impulses.
Structural Differences: Neurons have axons and dendrites; neuroglia are generally smaller and more numerous.
Functional Differences: Neurons transmit signals; neuroglia maintain the environment around neurons.

Structure of a Neuron

Cell Body (Soma): Contains the nucleus and organelles.
Dendrites: Receive incoming signals from other neurons.
Axon: Conducts impulses away from the cell body.
Axon Terminals: Release neurotransmitters to communicate with other cells.
Myelin Sheath: Insulating layer that increases the speed of impulse transmission.

Resting Potential and Action Potential

Neurons maintain a voltage difference across their membrane, known as the resting potential. An action potential is a rapid change in this voltage that allows signal transmission.

Resting Potential: The inside of the neuron is negatively charged relative to the outside. Typical value: .
Action Potential: A brief reversal of membrane potential, allowing the neuron to transmit a signal.

Location of Charges and Ions

Resting Potential: Negative inside, positive outside. More Na+ outside, more K+ inside.
Action Potential: During depolarization, Na+ rushes in, making the inside positive.

Repolarization

After an action potential, K+ ions move out, restoring the negative internal charge (repolarization).

Synaptic Transmission

Synapse: Junction between two neurons.
Synaptic Cleft: Small gap between the axon terminal of one neuron and the dendrite of another.
Neurotransmitters: Chemicals released into the synaptic cleft to transmit impulses.

Major Divisions of the Brain

Brain Stem: Controls basic life functions.
- Pons: Relays signals between cerebrum and cerebellum.
- Medulla Oblongata: Regulates heart rate, breathing, and blood pressure.
- Midbrain: Processes visual and auditory information.
Cerebellum: Coordinates movement and balance.
Diencephalon: Contains the thalamus (sensory relay) and hypothalamus (homeostasis, hormone regulation).
Cerebrum: Responsible for higher brain functions (thought, memory, voluntary movement).

Spinal Cord

Location: Extends from the base of the brain down the vertebral column.
Structure: Cylindrical bundle of nerve fibers.
Function: Transmits signals between the brain and the rest of the body; coordinates reflexes.

Cranial and Spinal Nerves

Cranial Nerves: 12 pairs; arise from the brain; control head and neck functions.
Spinal Nerves: 31 pairs; arise from the spinal cord; control body and limb functions.

Chapter 9: The Endocrine System

Functions of the Endocrine System and Hormones

The endocrine system regulates body activities by releasing hormones into the bloodstream. Hormones are chemical messengers that affect target cells or organs.

Exocrine vs. Endocrine Glands

Exocrine Glands: Secrete substances through ducts to the outside of the body or into the digestive tract (e.g., sweat glands).
Endocrine Glands: Release hormones directly into the bloodstream (e.g., thyroid gland).

Major Endocrine Glands and Their Hormones

Gland	Hormone(s)	Main Function(s)
Hypothalamus	TRH, oxytocin	Regulates pituitary gland; controls homeostasis
Pituitary Gland	GH, TSH, ADH, oxytocin	Master gland; regulates other glands
Thyroid Gland	TH, calcitonin	Regulates metabolism, calcium levels
Parathyroid Glands	PTH	Increases blood calcium
Pancreas	Insulin, glucagon	Regulates blood glucose
Adrenal Glands	Aldosterone, epinephrine	Regulates stress response, water balance
Pineal Gland	Melatonin	Regulates sleep-wake cycles
Kidneys	Erythropoietin	Stimulates red blood cell production

Hormones: Functions and Targets

Oxytocin: Stimulates uterine contractions and milk ejection.
Antidiuretic Hormone (ADH): Promotes water reabsorption in kidneys.
Growth Hormone (GH): Stimulates growth of bones and tissues.
Thyroid-Stimulating Hormone (TSH): Stimulates thyroid hormone release.
Thyroid-Releasing Hormone (TRH): Stimulates TSH release from pituitary.
Melatonin: Regulates circadian rhythms.
Thyroid Hormone (TH): Increases metabolic rate.
Calcitonin: Lowers blood calcium levels.
Parathyroid Hormone (PTH): Raises blood calcium levels.
Aldosterone: Increases sodium reabsorption in kidneys.
Epinephrine: Increases heart rate and energy during stress.
Insulin: Lowers blood glucose by promoting uptake into cells.
Glucagon: Raises blood glucose by stimulating glycogen breakdown.
Erythropoietin: Stimulates red blood cell production in bone marrow.

Chapter 10: Blood

General Characteristics and Functions of Blood

Blood is a connective tissue with vital roles in transport, regulation, and protection.

Functions: Transports gases, nutrients, and wastes; regulates pH and temperature; protects against disease and blood loss.

Properties of Blood

pH Range: 7.35–7.45
Volume: Approximately 5–6 liters in adults
Components:
- Plasma: Liquid matrix (about 55% of blood volume); contains water, proteins, nutrients, hormones.
- Formed Elements: Cells and cell fragments (about 45% of blood volume):
  - Erythrocytes (Red Blood Cells): Transport oxygen and carbon dioxide.
  - Leukocytes (White Blood Cells): Defend against infection.
  - Platelets (Thrombocytes): Involved in blood clotting.

Hemostasis: Prevention of Blood Loss

Hemostasis is the process that stops bleeding after injury.

Vascular Spasms: Blood vessels constrict to reduce blood flow.
Platelet Plug Formation: Platelets adhere to the injury site and form a temporary plug.
Coagulation: Fibrin threads reinforce the platelet plug, forming a stable clot.

Blood Typing and Transfusions

ABO Blood Groups: Determined by the presence of antigens (A, B) on red blood cells.
Antigens: Substances on cell surfaces that trigger immune responses.
Antibodies: Proteins in plasma that react with foreign antigens.
Importance: Correct blood typing prevents transfusion reactions.

Blood Type	Antigen(s)	Antibody(ies)	Can Receive From
A	A	Anti-B	A, O
B	B	Anti-A	B, O
AB	A, B	None	A, B, AB, O
O	None	Anti-A, Anti-B	O

Example: A person with type A blood has A antigens and anti-B antibodies; they can receive type A or O blood.

Additional info: Where details were not specified, standard academic context was added for completeness (e.g., functions of specific hormones, blood typing table).