Lecture 9 Brain and Hormones and Hormones and the Brain

How do neurotransmitters differ from hormones?

Neurotransmitters act across synapses, are fast-acting, and released by neurons; hormones travel via the bloodstream, act slower, and affect many cells.

What are the two major classes of hormones?

Amine/peptide hormones (water-soluble, protein-based) and steroid hormones (lipid-soluble, derived from cholesterol).

What is the role of hormone receptors?

Hormones bind to receptors to activate cellular events; receptors are as critical as the hormones themselves.

What is the role of the hypothalamus in the endocrine system?

It controls the pituitary gland and acts as a hormonal center influenced by the limbic system.

What does the anterior pituitary do?

It releases hormones under the brain’s control, regulating peripheral gland hormone release.

What does the posterior pituitary do?

It stores and secretes hormones made in the hypothalamus, like oxytocin and vasopressin.

What is the function of antidiuretic hormone (ADH)?

ADH helps retain water; alcohol inhibits it, leading to dehydration.

Name a hormone released by the heart and its function.

Atrial natriuretic factor (ANF) reduces blood volume and pressure by signaling kidneys to produce more urine.

How does Interleukin-1 act both hormonally and neurologically?

It triggers immune defense and affects the brain, causing fatigue, pain, and stress responses.

What is an example of endocrine system crosstalk?

The ovarian axis: LHRH → LH → estrogen release; stress can disrupt every step in this chain.

Name three neuronal effects caused by hormones.

Altered protein function/synthesis, changed neural structure (e.g., dendrites), and influenced neurogenesis.

What are glucocorticoids and when are they released?

Steroid hormones like cortisol released during stress.

How does stress affect dopamine?

Glucocorticoids modulate dopamine release, influenced by stress duration.

How do hormones affect dendritic structure?

 Estrogen enhances growth (especially in the hippocampus), while chronic stress causes shrinkage (especially in the hippocampus) and growth in the amygdala.

How do estrogen and glucocorticoids affect neurogenesis?

Estrogen enhances it and protects neurons; glucocorticoids inhibit it and reduce neuronal survival.

How does stress impact the amygdala?

It heightens function, increasing emotional reactivity and may contribute to PTSD.

How does stress affect the frontal cortex?

Impairs decision-making, risk assessment, emotional regulation, empathy, and increases selfish behavior.

How does stress affect the hippocampus?

Impairs working memory, weakens hippocampal-frontal links, enhances fear learning, and impairs fear extinction.

What does “contingent” hormone action mean?

Hormones don’t cause behaviors directly but modify the likelihood of preexisting tendencies under certain conditions.

Does testosterone cause aggression?

No; it amplifies existing amygdala activity but doesn’t initiate it.

How do glucocorticoids affect learning and memory?

Short-term: enhance LTP in hippocampus. Chronic: disrupt hippocampal LTP but enhance amygdala LTP (trauma encoding).

How can hormones lead to long-term behavioral changes?

Through synaptic plasticity (LTP) and organizational effects during critical developmental periods like puberty or prenatal stages.