Biological Psychology: Neurons, Neurotransmitters, and Hormonal Regulation

What is a chemical synapse?

A junction where neurotransmitters are released from one neuron to excite or inhibit the next neuron.

Who was the first person to isolate a chemical messenger?

Otto Loewi

What neurotransmitter is involved in deep breathing?

Acetylcholine (ACh)

What is the role of epinephrine (EP) in the body?

It mobilizes the body for fight or flight during times of stress.

What distinguishes neurotransmitters from hormones?

Neurotransmitters transmit signals through the nervous system, while hormones travel through the bloodstream.

What is the process of neurotransmission?

The process of transmitting information across a chemical synapse from the presynaptic neuron to the postsynaptic neuron.

What are the two classes of receptors for neurotransmitters?

Ionotropic receptors and metabotropic receptors.

What is the function of ionotropic receptors?

They allow rapid changes in membrane voltage, usually excitatory.

What is the function of metabotropic receptors?

They are slow-acting and trigger a series of intracellular events when activated.

What is homeostasis?

The maintenance of internal metabolic balance and regulation of physiological systems in an organism.

What is the role of glucocorticoids like cortisol during stress?

They mobilize the body's resources to confront a stressor and repair stress-related damage.

What is the stress response?

Physiological and behavioral arousal in response to a stimulus that challenges homeostasis.

What is the role of the enteric nervous system (ENS)?

It acts independently of the CNS and regulates gastrointestinal functions.

What neurotransmitter is primarily used by cholinergic neurons?

Acetylcholine (ACh)

What happens during the fight-or-flight response?

The sympathetic division of the ANS increases heart rate and decreases digestive functions.

What is the function of peptide neurotransmitters?

They act as hormones that respond to stress and regulate various physiological functions.

What is the significance of the vagus nerve?

It plays a key role in the transmission of acetylcholine (ACh) for deep breathing.

What are small-molecule neurotransmitters?

Quick-acting neurotransmitters synthesized in the axon terminal from dietary nutrients.

What is the role of the hippocampus in stress regulation?

It detects cortisol levels and signals the hypothalamus to reduce blood cortisol levels.

What is hyperglycemia?

High blood-glucose levels caused by insufficient insulin secretion.

What is hypoglycemia?

Low blood-glucose levels that can impair cellular function.

What is the dual role of hormones in the body?

Many hormones act as neurotransmitters, and many neurotransmitters act as hormones.

What are the four activating systems of the CNS?

The cholinergic, dopaminergic, noradrenergic, and serotonergic systems.

What neurotransmitter is associated with pleasure and reward?

Dopamine (DA)

What is the role of norepinephrine (NE) in the body?

It accelerates heart rate and is involved in the PNS division of the ANS.

What happens when cortisol levels are too high?

It can damage neurons in the hippocampus, leading to impaired stress regulation.

What is the primary function of homeostatic hormones?

To maintain internal metabolic balance.

What is the role of neurotransmitters in the somatic nervous system (SNS)?

They excite skeletal muscles to cause contractions.

What is the significance of the feedback loop involving cortisol?

Prolonged stress leads to excessive cortisol release, damaging hippocampal neurons.

5 steps of neurotransmission

1. synthesis: neurotransmitters are created from precursor modules

2. packaging and storage: neurotransmitters are moved into vesicles and await the arrival of an action potential

3. release: neurotransmitters is released across the membrane by exocytosis

4. receptor action: transmitters crosses the sypnatic cleft and binds to receptor

5. inactivation: transmitters diffuses away, is enzymatically degraded, is taken into the neuron terminal or taken up by an astrocyte

excitatory synapse

located on dendrites, round vesicles, dense materials on membranes, wide cleft, large active zone

inhibitory synapse

located on cell body, flat vesicles, sparse material on membranes, narrow cleft, and small active zone

classes of neurotransmitters

small-molecule transmitters

peptide transmitters

lipid transmitters

gaseous transmitters

ion transmitters

small molecule transmitters

synthesised in the axon terminal from dietary nutrients and packaged ready for use in axon terminals

• heart, parkinson’s, immune response

peptide neurotransmitters

amino-acid chains i.e cortisol, oxytocin (bonding between mom and infant), endorphins

is a neurotransmitter only a ssociated with one receptor?

no neurotransmitter is associated with a single receptor type

can different transmitters co-exist in the same terminal/synapse?

yes. a single neuron may use one transmitter at one synapse and a different transmitter at another synapse.

cholinergic neuron (motor neurons)

neuron that uses acetylcholine as its main neurotransmitter and excited skeletal muscles to cause contractions

nicotinic ACh receptor

when acetylcholine or nicotine binds to this receptor, its pore opens to permit ion flow, thus depolarising the muscle fiber

cholinergic system

active in maintaining attention and waking EEG pattern

noradrenergic system

active in maintaining emotional tone

dopaminiergic system

active in maintaining normal motor behaviour

serotonergic system

active in maintaing waking EEG pattern

hierarchical control of hormones

1. hypothalamus produces neurohormones which enter the anterior pituitary through veins and the posterior pituitary through axons.’

2. pituitary sends hormones into the bloodstream to target endocrine glands

3. endocrine glands release their own hormones that stimulate target organs, including the brain.

homeostatic hormone

maintain internal metabolic balance and regulate physiological systems in an organism

gonadal hormone

i.e testosterone

glucocorticoid

i.e cortisol

homeostasis

typical homeostatic function is controlling blood-sugar level and instruct glycogen synthase in liver/muscle cells to store glucose/glycogen

diabetes mellitus

caused by failure of the pancreas to secrete enough insulin

stressor

stimulus that challenges the body’s homeostasis and triggers arousal

stress response

physiological and behavioural arousal

fast stress response

primes the body immediately for fight or flight

slow stress response

both mobilises the body’s resources to confront a stressor and repairs stress-related damage (cortisol)

fast acting pathway to activating a stress response

1. hypothalamus sends a neural message through the spinal cord

2. sympathetic division of the autonomic nervous system is activated to stimulate the medulla of the adrenal gland

3. adrenal medulla releases epinephrine into the circulatory system

4. epinephrine activates the body’s cells, endocrine glands, and the brain

slow-acting pathway to activating a stress response

1. hypothalamus releases CRH into the pituitary gland

2. pituitary gland releases ACTH, which acts on the cortex of the adrenal gland

3. adrenal gland releases cortisol into the circulatory system

4. cortisol activates the body’s cells, endocrine glands, and the brain

how does unrelieved stress lead to a vicious cycle of damaged hippocampal neurons

Unrelieved stress promotes excessive cortisol release, which damages hippocampal neurons. These neurons cannot detect cortisol or signal the adrenal gland to stop producing it, leading to enhanced cortisol secretion.