Unit 6 Study Guide: Hormones, Reproduction, and Nervous Systems

Chapter 45: Hormones and the Endocrine System

Key Hormone Terminology

• Releasing hormone: Hormone from the hypothalamus that stimulates anterior pituitary hormone release.

• Inhibiting hormone: Hypothalamic hormone that suppresses pituitary hormone secretion.

• Tropic hormone: Hormone that targets another endocrine gland (e.g., TSH).

Hormones and Their Functions

• Hormones: Chemical messengers released into the bloodstream that regulate physiology, metabolism, growth, reproduction, and homeostasis.

Endocrine vs. Nervous System

• Endocrine system: Slow response, long-lasting effects.

• Nervous system: Fast response, short-lived effects.

Types of Signaling Mechanisms

Type	Secreted Molecule
Endocrine	Hormones into blood
Paracrine	Local regulators
Autocrine	Self-signaling molecules
Synaptic	Neurotransmitters
Neuroendocrine	Neurohormones

Endocrine vs. Exocrine Glands

• Endocrine glands: Ductless, secrete hormones into blood.

• Exocrine glands: Have ducts, secrete substances like sweat, enzymes, saliva.

Hormones, Neurohormones, and Neurotransmitters

• Hormone: Released by endocrine cells (e.g., insulin).

• Neurohormone: Released by neurons into blood (e.g., ADH).

• Neurotransmitter: Released at synapses for local signaling (e.g., acetylcholine).

Pheromones

• Chemical signals released into the environment affecting behavior of others (e.g., mate attraction).

Major Classes of Hormones

Class	Solubility
Peptide	Water-soluble
Amine	Usually water-soluble
Steroid	Lipid-soluble

Hormone Solubility and Receptor Location

• Water-soluble hormones: Bind to membrane receptors.

• Lipid-soluble hormones: Bind to intracellular receptors (cytoplasm or nucleus).

Cellular Responses to Hormones

• Water-soluble: Activate second messenger systems.

• Lipid-soluble: Alter gene transcription.

G Protein Coupled Receptors (GPCRs)

• Membrane receptors that activate G-protein signaling pathways (e.g., epinephrine uses GPCRs).

• GPCRs are used by water-soluble hormones.

Feedback Pathways

• Negative feedback: Reduces response (most hormones use this).

• Positive feedback: Amplifies response (e.g., oxytocin in childbirth).

Hormonal Control in Insects

• Ecdysone: Controls molting and metamorphosis.

• Juvenile hormone (JH): High JH leads to molting; low JH leads to metamorphosis.

Major Vertebrate Endocrine Glands and Hormones

Gland	Hormone	Effect
Hypothalamus	Releasing hormones	Controls pituitary
Pituitary	Many tropic hormones	Master gland
Thyroid	T3/T4	Metabolism
Parathyroid	PTH	Raises Ca2+
Adrenal	Cortisol, epinephrine	Stress response
Pancreas	Insulin, glucagon	Glucose control
Gonads	Sex hormones	Reproduction

Hypothalamus and Pituitary Gland

• Hypothalamus: Receives nervous input, initiates endocrine responses.

• Anterior pituitary: Produces hormones, controlled by releasing/inhibiting hormones.

• Posterior pituitary: Stores/releases hormones made in hypothalamus, controlled by neurons.

Posterior Pituitary Hormones

• ADH (antidiuretic hormone): Acts on kidneys to increase water reabsorption, reducing urine output.

• Oxytocin: Stimulates uterine contractions and milk release (positive feedback).

Anterior Pituitary Hormones

• GH, TSH, ACTH, FSH, LH, Prolactin (act on various tissues).

Thyroid Hormone Cascade Pathway

• Hypothalamus releases TRH → Pituitary releases TSH → Thyroid releases T3/T4.

• Negative feedback: T3/T4 inhibit TRH and TSH.

Thyroid Disorders

• Hypothyroidism: Low metabolism (e.g., Hashimoto’s disease—autoimmune destruction).

• Hyperthyroidism: High metabolism (e.g., Graves’ disease—overstimulation).

• Goiter: Enlarged thyroid, often due to iodine deficiency.

Growth Hormone Disorders

• Hyposecretion: Dwarfism.

• Hypersecretion: Gigantism/acromegaly.

Calcium Regulation

• PTH: Raises blood Ca2+.

• Calcitonin: Lowers blood Ca2+.

Adrenal Hormones

• Epinephrine/norepinephrine: Fight-or-flight response.

• Glucocorticoids: Metabolism and stress response.

• Mineralocorticoids: Salt and water balance.

• Same hormone can have different effects due to different receptors in tissues.

Sex Hormones

• Control sexual development, gamete production, and secondary sex characteristics.

Chapter 46: Animal Reproduction

Key Reproductive Terminology

• Sexual reproduction: Fusion of gametes from two parents.

• Asexual reproduction: Offspring arise from a single parent (cloning).

• Fission: Splitting of an organism into two.

• Budding: Offspring grows from parent body.

• Parthenogenesis: Development from an unfertilized egg.

• Fragmentation: Body breaks into pieces, each can regenerate.

• Regeneration: Regrowth of lost tissues.

• Hermaphroditism: Individual has both male and female reproductive organs.

• Sex reversal: Individual changes sex during life.

• Ovulation: Release of egg from ovary.

• Fertilization: Fusion of sperm and egg.

• Gametogenesis: Formation of gametes (sperm or eggs).

Sexual vs. Asexual Reproduction

• Two-fold cost of sex: Only females produce offspring, slowing population growth.

• Advantage of sexual reproduction: Genetic variation increases survival in changing environments.

Fertilization Types

• Internal fertilization: Fewer gametes, more protection (common in terrestrial animals).

• External fertilization: Many gametes, usually aquatic environments.

Male Reproductive System

• External organs: Testes, penis.

• Internal organs: Epididymis, vas deferens, urethra.

• Testes location: Outside abdominal cavity for cooler temperature needed for sperm production.

• Sperm pathway: Testis → Epididymis → Vas deferens → Urethra.

• Semen: Sperm plus glandular secretions.

Female Reproductive System

• External organs: Vulva (not listed but implied).

• Internal organs: Ovaries, oviducts (fallopian tubes), uterus, vagina.

• Ovulation: Egg released; remaining follicle becomes corpus luteum.

Gametogenesis

Process	Features
Spermatogenesis	Continuous, 4 sperm per precursor cell
Oogenesis	Cyclic, 1 egg per precursor cell, arrested stages

• Primary oocyte: Arrested in Prophase I.

• Secondary oocyte: Arrested in Metaphase II; completes meiosis after fertilization.

Hormonal Regulation of Reproduction

• GnRH: Stimulates FSH and LH release from anterior pituitary.

• FSH: Stimulates sperm and follicle development.

• LH: Stimulates testosterone production and ovulation.

• Sertoli cells: Secrete inhibin in response to FSH (negative feedback).

• Leydig cells: Secrete testosterone in response to LH.

Female Reproductive Cycles

• Ovarian cycle: Follicle development, ovulation, corpus luteum formation.

• Uterine cycle: Endometrial changes (proliferative, secretory, menstrual phases).

• LH surge: Triggers ovulation.

• Estradiol: Produced by developing follicle.

• Corpus luteum: Produces progesterone; degenerates if no fertilization, leading to menstruation.

Hormonal Feedback in Female Cycle

• High estradiol and progesterone inhibit LH and FSH (negative feedback).

Embryonic Development

• First trimester: Organ formation.

• Second trimester: Growth.

• Third trimester: Final maturation.

• Labor hormones: Oxytocin and prostaglandins stimulate contractions (positive feedback).

Chapter 48: Neurons, Synapses, and Signaling

Key Nervous System Terminology

• Presynaptic cell: Sends signal.

• Postsynaptic cell: Receives signal.

• Membrane potential: Voltage across cell membrane.

• Resting potential: −70 mV (typical neuron).

• Depolarization: Na+ enters cell, membrane potential becomes less negative.

• Hyperpolarization: K+ exits cell, membrane potential becomes more negative.

• Action potential (AP): Rapid, all-or-none electrical signal.

• Threshold: −55 mV (typical value for AP initiation).

• Refractory period: Time after AP when neuron cannot fire again.

• Myelin sheath: Insulating layer around axons.

• Nodes of Ranvier: Gaps in myelin sheath where APs are regenerated.

• Saltatory conduction: AP jumps from node to node, increasing speed.

• EPSP: Excitatory postsynaptic potential (depolarizing).

• IPSP: Inhibitory postsynaptic potential (hyperpolarizing).

• Temporal summation: Multiple signals in quick succession.

• Spatial summation: Multiple signals from different synapses.

Nervous System Organization

• CNS: Brain and spinal cord.

• PNS: All peripheral nerves.

Neuron Anatomy

• Dendrites → Soma (cell body) → Axon → Axon terminals.

Synapse Function

• Electrical signal triggers neurotransmitter release, which binds to receptors on postsynaptic cell.

Information Processing Stages

• Sensory input → Integration → Motor output.

Glial Cells

• Support neurons, maintain environment, form myelin, immune defense.

Ion Concentrations and Resting Potential

• Na+ higher outside, K+ higher inside neuron.

• Resting potential maintained by Na+/K+ pump and ion leakage.

Action Potential Phases

1. Resting state

2. Depolarization (Na+ influx)

3. Repolarization (K+ efflux)

4. Hyperpolarization

5. Return to rest

• APs are all-or-none and travel in one direction due to refractory period.

• Larger axon diameter and myelination increase conduction velocity.

Chemical Synapses and Neurotransmitters

• EPSPs depolarize, IPSPs hyperpolarize postsynaptic cell.

• Summation at axon hillock determines if AP is generated.

• Neurotransmitter signaling terminated by reuptake or enzymatic breakdown.

Neurotransmitter Classes

Class	Examples	Notes
Acetylcholine	Acetylcholine	Common excitatory
Amino acids	Glutamate, GABA	CNS function
Biogenic amines	Dopamine, serotonin	Modulatory roles
Neuropeptides	Short AA chains	Modulate activity
Gases	NO, CO	Diffuse signaling

Chapter 49: Nervous Systems

Key Nervous System Terminology

• Nerves: Bundles of axons.

• Ganglia: Clusters of neuron cell bodies in PNS.

• Gray matter: Neuron cell bodies.

• White matter: Myelinated axons.

• Cerebrospinal fluid (CSF): Cushions brain and spinal cord.

• Lateralization: Specialization of brain hemispheres.

• Neuronal plasticity: Brain's ability to rewire connections.

CNS vs. PNS

• CNS: Integration and processing.

• PNS: Sensory and motor pathways.

Reflexes

• Automatic, rapid responses via spinal cord (bypass brain).

Afferent vs. Efferent Neurons

• Afferent: Sensory input to CNS.

• Efferent: Motor output from CNS.

PNS Efferent Branches

• Somatic (motor) system

• Autonomic nervous system (sympathetic, parasympathetic, enteric)

Autonomic Nervous System Divisions

Division	Function
Sympathetic	Fight or flight
Parasympathetic	Rest and digest
Enteric	Digestive tract regulation

Glial Cell Functions

• Ependymal cells: Produce CSF.

• Microglia: Immune defense.

• Astrocytes: Support neurons.

• Oligodendrocytes: Myelinate CNS axons.

• Schwann cells: Myelinate PNS axons.

Blood-Brain Barrier

• Protects brain from toxins and pathogens.

Brain Development and Structure

• Embryonic regions: Forebrain (cerebrum, thalamus, hypothalamus), midbrain (relay center), hindbrain (cerebellum, pons, medulla).

• Corpus callosum: Connects cerebral hemispheres.

• Cerebrum: Higher functions; divided into left and right hemispheres.

• Diencephalon: Thalamus (sensory relay), hypothalamus (homeostasis), epithalamus.

• Cerebellum: Coordination and balance.

• Brainstem: Midbrain, pons, medulla (basic life functions).

• Reticular formation: Regulates arousal and sleep.

• Limbic system: Emotion and memory (includes hippocampus, amygdala).

Cerebral Cortex Lobes and Functions

Lobe	Function
Frontal	Decision making, motor control
Parietal	Touch, spatial processing
Temporal	Hearing, language
Occipital	Vision

• Thalamus: Directs sensory input to cortex.

• Hippocampus: Short-term memory.

• Cerebral cortex: Long-term memory storage.