Reproductive System & Endocrine Glands

• These notes review the parts and functions of the endocrine system, nervous system, female and male reproductive systems, and feedback mechanisms (homeostasis).

Endocrine System

• Endocrine glands secrete hormones directly into the bloodstream for long-term control of target organs, and are ductless.
• Exocrine glands secrete enzymes into ducts for short-term control, sending those enzymes to target tissues.
• Glands produce and release substances for specific bodily functions.
• Hormones are chemical messengers secreted by glands into the blood, affecting cells in other parts of the body.

Feedback Mechanisms

• Negative feedback reduces changes to maintain stability, regulating homeostasis by halting hormone production when enough is present.
• Positive feedback increases process rates based on sensor information, exacerbating deviations from a set point.

Glands

• The pituitary gland, known as the master gland, regulates other endocrine glands and body functions.
• The posterior pituitary gland releases hormones produced by the hypothalamus, including oxytocin and antidiuretic hormone (ADH).
• Oxytocin plays a crucial role in childbirth by stimulating uterine contractions and promotes milk ejection during breastfeeding.
• ADH (Vasopressin) helps the body maintain water balance by increasing water reabsorption in the kidneys.
• The anterior pituitary gland receives releasing factors from the hypothalamus through portal vessels.
• Growth Hormone (GH) controls body growth and development, especially of bones and muscles, where abnormalities could result in dwarfism or gigantism.
• Thyroid-stimulating hormone stimulates the thyroid gland to produce thyroid hormones (T3 and T4), which regulate metabolism, energy production, and overall growth.
• Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce and release cortisol which is a stress hormone that helps the body respond to stress, maintain blood pressure, and regulate metabolism.
• Prolactin (PRL) promotes milk production in lactating females.
• Melanocyte-stimulating hormone influences pigmentation by stimulating melanin production in skin cells.
• Follicle-stimulating hormone promotes the growth and maturation of ovarian follicles in females and stimulates sperm production in testes in males.
• Luteinizing hormone triggers ovulation and the formation of the corpus luteum in females, and stimulates testosterone production in testes in males.
• The butterfly-shaped thyroid gland in the neck regulates metabolism, energy production, and growth.
• Thyroxine (T4) is the primary hormone produced by the thyroid, containing 4 iodine atoms.
• Triiodothyronine (T3) contains 3 iodine atoms and is more potent than T4.
• Calcitonin helps regulate calcium levels in the blood.
• The thyroid gland increases the basal metabolic rate, regulates growth and development, converts food to energy, and affects body temperature and heart rate.
• Hypothyroidism is when the thyroid doesn't produce enough thyroid hormone.
• Hyperthyroidism is when the thyroid gland produces too much thyroid hormone.
• Ghrelin is a hunger hormone with many bodily functions, and is produced and released mainly in the stomach.
• Leptin is a hormone that signals when you're full.
• Melatonin regulates the sleep-wake cycle, carcadian rhythm.
• Serotonin also tells you when you are full.
• The pancreas regulates blood sugar levels and aids in food breakdown.
• The pancreas functions as part of the exocrine system (digestive role), producing digestive enzymes to break down carbohydrates, proteins, and fats in the small intestine.
• The endocrine system of the pancreas regulates blood sugar levels, while it produces hormones to control blood glucose levels.
• Insulin lowers blood sugar by facilitating glucose uptake into cells.
• Glucagon raises blood sugar by signaling the liver to release stored glucose.
• Dysfunction of the pancreas can lead to diabetes.
• Adrenal glands produce hormones that help regulate metabolism, the immune system, blood pressure, stress response, and other functions.
• Cortisol is a stress hormone, and helps regulate metabolism, reduces inflammation, assists in the body’s stress response, while also maintaining blood sugar levels.
• Adrenaline (epinephrine) prepares the body for a fight-or-flight response, increasing heart rate, dilating airways, and boosting blood flow.
• Noradrenaline (norepinephrine) works alongside adrenaline in response to stress, focusing on maintaining blood pressure.
• Ovaries, located on either side of the uterus, produce and release eggs for fertilization and prepare eggs for release while also facilitating ovulation, where a mature egg is released.
• Estrogen aids the growth of the uterine lining during the first half of the menstrual cycle and is involved in bone density maintenance and skin health.
• Progesterone prepares the uterine lining for pregnancy and regulates the menstrual cycle.
• Testes produce sperm cells for reproduction and secrete testosterone, promoting the development of secondary sexual characteristics.

Nervous System

• The brain is the center of thoughts, the interpreter of the external environment, and the origin of control over body movement, processing sensory information, thoughts, emotions, and controlling bodily functions.
• The spinal cord acts as a highway for information traveling between the brain and the body, sending instructions from the brain and carrying sensory information back.
• The central nervous system consists of the brain and spinal cord.
• The cerebellum coordinates voluntary and involuntary movements, helps in learning and remembering, and adjusts muscles to maintain posture.
• The brain stem connects the spinal cord to the remainder of the brain and consists of the medulla oblongata, pons, and midbrain.
• The medulla oblongata contains discrete nuclei that regulates heart rate, blood vessel diameter, breathing, swallowing, coughing, and sneezing.
• The pons, also known as the bridge, is immediately superior to the medulla oblongata and contains several nuclei of the medulla oblongata.
• The midbrain involves visual reflexes and controls eye movements and pupil diameter.
• The cerebrum controls skeletal contractions and is the center for learning, emotion, memory, and perception.
• The cerebral cortex, the outer layer of the cerebrum, is vital for perception, voluntary movement, and learning.
• The left side of the cerebral cortex receives information from and controls the right side of the body, and vice versa, and a thick band of axons known as the corpus callosum connects the two.
• The frontal lobe processes voluntary muscle movements and is involved in planning and organizing behavior and decision-making.
• The parietal lobe processes information related to touch and is involved in self-awareness.
• The occipital lobe processes information from the eyes.
• The temporal lobe processes information from the ears and nose (olfactory and auditory).
• The limbic system (diencephalon) deals with emotions, memories, and arousal.
• The thalamus detects and relays sensory information, located between the brainstem and part of the pathway of information into the cerebrum.
• The amygdala prepares the body for emergency situations, stores memories, and influences decisions.
• The hippocampus converts short-term memories into long-term memories, stores new information, and recalls information.
• The hypothalamus maintains homeostasis, controlling body temperature, hunger, and thirst, and controls the secretion of hormones from the pituitary gland as well as sensations such as sexual pleasure and feeling relaxed.
• The peripheral nervous system allows the brain and spinal cord to receive and send information to other areas of the body.
• Peripheral nervous system connects the central nervous system to the organs, limbs, and skin, carrying sensory and motor information to and from the central nervous system.
• Sensory (afferent) nerves detect sensations like pain and heat and transmit messages to the CNS.
• Motor (efferent) nerves transmit messages away from the CNS and stimulate effectors to perform functions or reflexes.
• Reflex arcs involve sensory detection, interpretation of sensory input, and motor output.
• Ganglia are collections of sensory neuron soma.
• The somatic nervous system transmits sensory information and controls voluntary movements, connecting the central nervous system to the body’s muscles.
• The autonomic nervous system regulates involuntary movements such as heartbeat, digestion, and breathing.
• The sympathetic nervous system regulates the fight-or-flight response, preparing the body to expend energy in response to threats.
• The parasympathetic nervous system maintains normal body functions and conserves physical resources, slowing heart rate, slowing breathing, reducing blood flow to muscles, and constricting pupils after a threat has passed.

Reproductive System

• The purpose of the reproductive system is to produce gametes (egg and sperm cells), store and transport these cells, nurture offspring during development, and produce hormones.
• The female reproductive system produces eggs in the ovaries, which are transported via the oviducts (fallopian tubes).
• A sperm can fertilize the egg to produce an embryo, which can implant in the uterus and develop into a baby.
• The ovaries produce eggs and hormones (estrogen and progesterone).
• The oviducts (fallopian tubes) transport eggs, where the fertilization occurs.
• The uterus nurtures the developing fetus.
• The cervix connects the uterus to the vagina while acting as a passageway for delivering baby.
• The vagina functions both as the birth canal and where the female reproductive organs receive the sperm cells, while also being a sight for sexual intercourse.
• The corpus luteum releases progesterone for preparation over possible pregnancy (fertilization), where if there is no fertilization lutein (luteinizing) development will ensure development for the offspring, and the menstrual cycle occurs if non.
• Progesterone thickens the uterine lining where an embryo or baby can be stored.
• Sperm cell journey goes from the testes or male gonad -> sperm cell -> epididymis -> vas deferens (tube like urethra) -> ejaculation -> to female body -> vagina + cervix -> oviducts where it meets with the egg cell for fertilization
• Male external reproductive organs include the penis, scrotum, and testicles.
• The penis functions as a tube where sperm cells and urine exit the body, and enters the vagina for sexual intercourse.
• The scrotum regulates temperature, being looser in warmer temperatures and more compact during colder weather, due to keeping temperature 2° cooler than any other body parts
• The testicles store the sperm cells.
• Fructose provides energy to transport the sperm cell out.
• Sperm cells contain the mitochondria to produce power/energy.
• Sperm cells can die from the acidity of urine, however this is neutralized through other bodily functions.