Endocrine System

The endocrine system is a network of glands that produce and release hormones. These
hormones regulate key bodily functions such as metabolism, growth, development, mood, and
reproduction. Hormones travel through the bloodstream and affect various organs and tissues
to maintain homeostasis.

Major Endocrine Glands and Their Functions:

Gland Function Hormones Location

Oxytocin, Growth
Stimulates growth, At the base of the
Pituitary Hormones (GH),
controls other glands brain
Prolactin (PRL), etc.
Regulates
Front of the neck,
Thyroid metabolism and Thyroid hormone
below the voice box
calcium storage
Controls calcium
Parathyroid levels, normalizes Parathormone In the neck
bone growth
Produces T cells
Thymus Thymosin In front of the heart
before puberty
Affects metabolism,
Adrenal immune system, Adrenaline, others On top of the kidneys
blood pressure
Regulates blood
Pancreas Insulin, Glucagon Behind the stomach
sugar levels
Controls sperm
maturation, male
Testes Testosterone In the scrotum
secondary
characteristics
Influences female
secondary Estrogen,
Ovaries In the pelvic area
characteristics, egg Progesterone
maturation
Regulates biological
Pineal Melatonin In the brain
clock

Role of Hormones in Reproductive Systems:

Male:

 Pituitary Gland: Releases FSH and LH

 FSH: Stimulates Sertoli cells for sperm nourishment

  LH: Stimulates Leydig cells to produce testosterone

 Testosterone: Develops male secondary characteristics, sperm production

Female:

 Pituitary Gland: Releases FSH and LH

 Ovaries:

o Estrogen: Controls egg growth and release

o Progesterone: Prepares uterus, prevents muscle contraction

 Inhibin: Inhibits FSH production

 FSH & LH: Regulate estrogen-progesterone levels, follicle development, ovulation

Endocrine System Disorders:

 Osteoporosis: Reduced bone mineral density, caused by parathyroid hormone

imbalance

 Goiter: Abnormal thyroid gland enlargement, due to thyroid hormone imbalance

 Gigantism: Abnormal height increases due to excessive growth hormones during

childhood

 Dwarfism: Short stature due to insufficient growth hormones in the pituitary gland

Menstrual Cycle

The menstrual cycle is a monthly series of changes that prepare a woman's body for potential
pregnancy. It involves a complex interaction between the hypothalamus, pituitary gland, and
gonads (ovaries). The average cycle lasts 28 days and consists of two main phases: the follicular
phase and the luteal phase.

Phases of the Menstrual Cycle:

1. Follicular Phase:

 Duration: Day 1 to Day 14 (starts on the first day of menstruation and ends with
ovulation)

 Hormones:
 o FSH (Follicle Stimulating Hormone): Stimulates follicular growth in ovaries,
leading to estrogen production

o Estrogen: Thickens the endometrium (uterine lining) and signals the release of
LH

o LH (Luteinizing Hormone): Triggers ovulation

 Key Events:

o Follicles in ovaries grow and mature

o Uterine lining thickens

o Ovulation occurs mid-cycle (around day 14)

2. Luteal Phase:

 Duration: Day 15 to Day 28 (from ovulation to the day before the next period)

 Hormones:

o Progesterone: Produced by the corpus luteum, thickens the endometrium, and

inhibits FSH and LH

o LH and FSH: Levels decrease after ovulation

 Key Events:

o Corpus luteum forms from the empty follicle

o Endometrium continues to thicken

o If fertilization does not occur, the corpus luteum degenerates, leading to a

decrease in estrogen and progesterone levels

o Premenstrual syndrome (PMS) symptoms may occur

Hormones and Their Functions:

Gland Hormone Function

Stimulates follicular growth
FSH (Follicle Stimulating
Anterior Pituitary and estrogen secretion in
Hormone)
ovaries
Causes ovulation, triggers
corpus luteum formation,
Anterior Pituitary LH (Luteinizing Hormone)
stimulates progesterone
secretion
Ovaries Estrogen Thickens endometrium,
 stimulates LH release, stops
FSH production
Thickens endometrium,
Ovaries Progesterone inhibits FSH and LH during
the luteal phase
Gland Hormone Function

Important Points:

 Menstruation marks the start of a new cycle.

 Ovulation occurs around the midpoint of the cycle.

 The menstrual cycle continues for about 40 years, pausing during pregnancy and
resuming after childbirth.

 Seek medical attention if experiencing excessive pain during menstruation.

Nervous System

The nervous system is the body's control system and information storage center. It is
responsible for controlling and coordinating all the organ systems by sending messages from the
brain through nerve signals, ensuring that all parts of the body work together efficiently.

Major Divisions and Parts of the Nervous System:

1. Central Nervous System (CNS):

 Components: Brain and Spinal Cord

 Functions:

o Brain: Organizer and distributor of information, has three main parts:

 Cerebrum: Controls activity and thought.

 Cerebellum: Controls posture, balance, and coordination.

 Brain Stem: Connects the brain to the spinal cord, controls automatic
functions (breathing, digestion, heart rate, blood pressure).

o Spinal Cord: Channel for signals between the brain and body, controls simple
reflexes.

2. Peripheral Nervous System (PNS):

 Components: Somatic Nervous System and Autonomic Nervous System

  Functions:

o Somatic Nervous System: Voluntary control of body movements.

 Spinal Nerves: Carry motor and sensory signals between the spinal cord
and body.

 Cranial Nerves: Carry information to and from the brain stem.

o Autonomic Nervous System: Involuntary control of body movements.

 Sympathetic Nervous System: Activated during stress (increased heart

rate, breathing, dilation of pupils, sweating).

 Parasympathetic Nervous System: Maintains body functions, restores

normal or relaxed mode.

Nerve Cell (Neuron):

 Structure:

o Cell Body: Contains the nucleus.

o Dendrites: Carry impulses toward the cell body.

o Axons: Carry impulses away from the cell body.

o Synapse: Gap between neurons where communication occurs.

Maintaining Homeostasis:

 The nervous system provides quick responses to maintain homeostasis by regulating

body temperature, blood pressure, pH, and glucose concentration.

 The nervous system works with the endocrine system to maintain body equilibrium.

 Feedback Mechanisms:

o The brain receives messages about internal changes and works to restore normal
state.

o Hypothalamus affects the pituitary gland to secrete hormones, reaching specific

organs to restore homeostasis.

 Key Processes Maintained:

o Body temperature

o Water balance
o Metabolic waste levels

o Blood calcium levels