3 - Controlling Organ System Flashcards
What is the main role of the brain in the CNS
It acts as the main switching unit of the central nervous system (CNS)
What is the function of the spinal cord
Links the brain to the rest of the body and acts as a minor coordinating centre for simple reflexes
Where is afferent sensory information processed
In the somatic sensory nuclei
How are efferent motor signals delivered to muscles and glands
Through the ventral root from the somatic motor nuclei
What does the ANS regulate
Muscles in the skin, around blood vessels, in the eye, stomach, and heart, as well as glands
How is the ANS controlled
By the hypothalamus and medulla; it functions in an involuntary, reflexive manner
What are the two main types of acetylcholine receptors
Nicotinic receptors (excitatory, fast depolarisation) and muscarinic receptors (either excitatory or inhibitory, slow responses)
What type of synapses use noradrenaline and what are its effects
Adrenergic synapses; can be excitatory or inhibitory depending on the receptor type
Where are alpha1 receptors located and what do they do
On blood vessels to the skin, mucosa, and abdominal viscera
Vasoconstriction (excitatory)
Where are beta1 receptors located and what is their effect
In the heart; increase heart rate (excitatory)
Where are beta2 receptors located and what is their effect
On respiratory airways and blood vessels to skeletal muscle and the heart
Cause relaxation (inhibitory)
What is dopamine’s role in the CNS
Controls movement (excitatory or inhibitory); dopamine deficiency leads to Parkinson’s symptoms
How does cocaine affect dopamine
Inhibits its reuptake, increasing its presence in the synapse and causing feelings of intense pleasure
How does nicotine affect the ANS
It activates both the sympathetic and parasympathetic systems equally
What is the structure of sympathetic nerves
Short preganglionic fibres, long postganglionic fibres; ganglia are close to the spinal cord
What is divergence in the sympathetic system
One preganglionic fibre can influence many ganglia, allowing widespread, complex responses
What neurotransmitters are used in the sympathetic division
Preganglionic fibres release acetylcholine
Most postganglionic fibres release noradrenaline
Some release acetylcholine or nitric oxide
When is the sympathetic system most active
During stress, exertion, or emergencies (“fight or flight” response)
How are parasympathetic fibres organised
Less divergent; preganglionic fibres synapse on neurons in the same ganglia, targeting specific organs
What type of receptors do ganglionic neurons have in the parasympathetic system
Nicotinic receptors (respond to acetylcholine)
What receptors are found on parasympathetic effector tissues
Muscarinic receptors, which can produce high or low responses depending on the signalling pathway
What is the structural difference between the sympathetic and parasympathetic systems
The sympathetic system has widespread effects; the parasympathetic system has more targeted, local effects
How do visceral reflexes compare to somatic reflexes
They share similar components but are always polysynaptic and can be short or long reflexes
What is autocrine signalling
A hormone acts on the same cell that secreted it
What is paracrine signalling
A hormone affects nearby cells via interstitial fluid
What is endocrine signalling
Hormones are released into the bloodstream to act on distant target cells
What is neurocrine signalling
Hormones are produced by neurons, travel down axons, and are released into the bloodstream
What are the three main types of hormones
Amino acid derivatives – water soluble
Peptides and proteins – water soluble
Lipid-derived hormones – lipid soluble
What are the properties of lipid-derived hormones
Synthesised on demand from cholesterol
Not stored in cells
Released by simple diffusion
Carried in the blood bound to serum proteins
Which hormones act on intracellular receptors
Steroid and thyroid hormones (slow-acting, long-lasting)
Which hormones act on membrane receptors
Peptides, proteins, and amino acid hormones (fast-acting, short-lasting)
What are the 3 ways the hypothalamus controls endocrine function
- Secretes releasing hormones to control the anterior pituitary
- Controls sympathetic output to the adrenal medulla
- Produces ADH and oxytocin
How is endocrine secretion usually regulated?
Through negative feedback, often initiated by hypothalamic releasing hormones
How is growth hormone (GH) uniquely regulated
The hypothalamus produces both a releasing hormone and an inhibiting hormone
One is stimulated while the other is suppressed
What factors influence hypothalamic releasing hormone secretion (3)
- CNS inputs
- Levels of other hormones
- Environmental factors such as stress, feeding, temperature, exercise, and sleep cycles
Where are pancreatic endocrine cells located
A drop in blood glucose levels
What do pancreatic alpha cells secrete
Glucagon
What do pancreatic beta cells secrete
Insulin
What do pancreatic delta cells secrete
Somatostatin
What do pancreatic F cells secrete
Pancreatic polypeptide
What is the structure of insulin
A peptide hormone with two chains – alpha (21 amino acids) and beta (30 amino acids)
What are the rapid effects of insulin
Increases glucose, amino acid, and potassium uptake into insulin-sensitive cells (seconds)
What are the intermediate effects of insulin
Stimulates protein synthesis, inhibits protein breakdown, promotes glycogen formation, and inhibits gluconeogenesis (minutes)
What are the delayed effects of insulin
Increases mRNA for lipogenic and other enzymes (hours)
What triggers glucagon secretion
A drop in blood glucose levels
What are the primary effects of glucagon
Stimulates gluconeogenesis (glucose from lactate)
Mobilises glycogen from the liver (glycogenolysis)
What are the secondary effects of glucagon
Increases lipolysis (fat breakdown in adipose tissue)
Stimulates insulin release to help new glucose enter cells
