Module 1 pre-lab / lab Flashcards
What are the main functions of the following parts of the brainstem?
Midbrain Areas for visual and auditory reflexes, controls movements and relays motor impulses to important reflex integration.
Pons Sleep centre and important respiratory centre main connection between cerebellum/spinal cord and higher brain centres.
Medulla Ascending and descending pathways and important reflex integration areas - cardiac centre, vasomotor, respiratory, swallowing, vomiting, etc.
Describe the differences between an exocrine and endocrine gland.
Endocrine are ductless glands which secrete their products hormones directly into the blood,
exocrine have ducts which collect the secretions and direct to the point of release.
What is a tropic hormone and give an example?
A hormone whose action is to stimulate the release of other hormones from their target cells.
E.g., Anterior pituitary hormone secretes TSH (thyroid stimulating hormone) causing the cells of
the thyroid gland to secrete the two hormones T3/T4.
Define the following terms and give an example of each.
autocrine, paracrine and endocrine
Autocrine Affect the same cell that secretes them. White blood cells during infection.
Paracrine Affects neighbouring cells. GUT cells that secrete histamine.
Endocrine Affect cells some distance from source. Pituitary, gonads (testis, ovaries), etc.
Examine the table and summarise your findings in terms of hormone solubility based on chemical class and method of action on target cells.
Amino acid (except T3/4), peptides and proteins are all water soluble.
Steroid hormones are all lipid soluble.
Water soluble hormones use the indirect method of action on target cells.
Lipid soluble hormones use the direct method of action.
Define a reflex.
A reflex is an involuntary response to a stimulus, it is rapid, predictable and unlearnt.
What is the difference between a somatic reflex and an autonomic reflex?
Somatic reflex - Has skeletal muscle as the effector e.g. The muscles of the back in keeping your posture
Autonomic reflex - Involves smooth muscles, cardiac
muscle or body organs as the effector e.g. the constriction of the smooth muscle in the walls of blood vessels to maintain blood pressure
important reflexes in brainstem parts
1 Medulla
Vital reflexes including regulating heart rate, blood vessel
diameter, respiration, swallowing, vomiting, hiccupping,
coughing and sneezing
2 Pons Important respiratory centres involved with “switching between inspiration and expiration”.
3 Midbrain Visual and auditory reflexes e.g., The startle reflex
The hypothalamus is the main visceral control centre and has some importantfunctions in relation to homeostatic mechanisms. List as many functions as possible.
Regulation of food intake, regulate water and thirst, regulate cardiac/ smooth muscle, part of
limbic system, regulate body temperature, regulate sleep/wake cycles, control endocrine function
The hypothalamus is also an important link between the nervous system and the endocrine system. Explain its functional association to anterior pituitary and the posterior pituitary.
Anterior Pituitary: The hypothalamus secretes releasing and inhibiting hormones to exert
control the anterior Pituitary.
Posterior Pituitary: The hypothalamus manufactures two hormones (ADH and oxytocin) that
are released from the posterior pituitary
The pituitary gland lies directly below, and is functionally controlled by, which region of the
brain?
Hypothalamus
pituitary is connected to hypothalamus by which structure
Infundibulum (pituitary stalk)
Which lobe of the pituitary is larger?
Anterior
What proportion of the total gland does it represent? anterior?
~70-80%
Describe the embryological origin of the anterior pituitary? (i.e., where did it develop from?)
Develops from epithelia tissue in the roof of the mouth and migrates to its final position
Releasing/inhibiting factors (hormones) control the synthesis and secretion of anterior pituitary
hormones.
Which area of the brain are these releasing/inhibiting hormones secreted from?
Hypothalamus
What type of connection (vascular or neural) exists between the hypothalamus and the anterior
pituitary?
Vascular
What is the name of this vascular connection?
Hypothalamo-hypophysial portal system
Complete the table below on the anterior pituitary hormones and their target tissues.
1 Growth hormone - Most body tissues
2 Thyroid stimulating - hormone Thyroid Gland
3 Follicle stimulating hormone - The Gonads (ovaries & testis)
4 Luteinizing hormone - The Gonads
5 Prolactin - Ovaries and mammary glands
6 Adrenocorticotropic hormone - Adrenal gland (cortex only)
7 Melanocyte stimulating hormone - Melanocytes in the skin
What type of connection (vascular or neural) exists between the hypothalamus and the
posterior pituitary?
Neural
What is the name of this neural connection/tract?
Hypothalamo-hypophysial tract
Which two hormones does the posterior pituitary secrete?
i. Oxytocin
ii. Anti-Diuretic Hormone (ADH)
Name the target tissue/glands for these two posterior pituitary hormones?
i. Uterus and mammary glands (Oxytocin)
ii. The kidneys (ADH)
The thyroid gland is located in which region of the body?
Neck
thyroid gland is located anterior to which structure?
Trachea/Larynx
Identify the regions labelled on the model of thryoid gland
- Right lobe
- Left lobe
- Isthmus
The two hormones synthesised by and secreted from these structures that regulate metabolic
rate are:
i. T3 (triiodothyronine)
ii. T4 (thyroxine)
What is the generalise function of these T3 and T4 hormones?
To alter metabolic rate of most cells as well as growth and maturation in others
Which hormone controls the release of thyroid hormones and where is itsecreted?
TSH (Thyroid stimulating hormone), which is secreted from the Anterior pituitary.
The hormone parafollicular cells secrete is called?
Calcitonin
What is the function of this hormone? (calcitonin)
↓ Blood Ca++ by promoting Ca++ deposition in bone & ↑ renal Ca++ excretion
The hormone the parathyroid glands secrete is called
Parathyroid hormone
What is the function of this hormone? (PTH)
Increases blood calcium levels by promoting Ca release from bone, decreasing Ca excretion and
increasing active Vitamin D and so increasing Ca absorption in the gastrointestinal tract
Why do you think the body produces two hormones to control blood Ca++
To ensure blood Ca++ levels are tightly controlled within tolerable limits
Can you think of any other substance that is controlled by twohormones?
Blood glucose (controlled by insulin and glucagon)
Where are the adrenal glands located?
Superior to each kidney
What shape is the adrenal gland?
Flattened pyramid
Aldosterone is responsible for the retention of which important ion by the kidneys?
Sodium (Na+)
Cortisol can increase the blood levels of which substance?
Glucose (for energy)
All the hormones secreted by the adrenal cortex are steroid based hormones, howwould they
work on their target cell?
Steroid hormones are lipid soluble, they can dissolve through the cell membrane of the target
cells using the direct method of action by attaching onto a receptor located inside the cell either
in the cytoplasm or in the nucleus
What two hormones are secreted by the adrenalmedulla?
Epinephrine (adrenaline) and norepinephrine (noradrenaline)
Which division of the nervous system stimulates their release?
Sympathetic nervous system
In what type of situation would you predict that these hormones would bereleased?
Short term stress – flight, fright, fight, etc.
What class of hormones (amino acid, peptide, protein, steroid or fatty acids) are those from the adrenal medulla?
Amino acid
The target cells for these hormones have their hormone receptor located where, inside the cell
or on the cell membrane surface?
As these hormones are water soluble they would use the indirect mechanism of hormone action –
therefore the hormone receptor would be located on the cell membrane.
In which body cavity is the pancreas located? (pancreas)
Abdominal
Approximately how long is the gland? (pancreas)
12.5-15cm
Name the part of the small intestine that is closest to the head of the pancreas
The duodenum
Name the organ that is lateral to the tail of the pancreas
The spleen
The pancreas is an unusual gland in that it has both exocrine and endocrine functions. Explain
the difference between the two and relate it to the structure and function of the pancreas.
The exocrine pancreas secretes substances for the process of digestion and uses a duct to
transport them from the pancreas to the small intestine (duodenum), while the endocrine
secretes its products into the cardiovascular system for distribution around the body.
The islets are composed of several types of secretory cells, name the two main cell types and
their respective secretions.
Alpha - Glucagon
Beta - Insulin
response of glucagon and insulin
Glucagon - Release of glucose into the blood, increase breakdown of glycogen.
Insulin - Increase uptake of glucose and amino acids into body cells (liver, adipose, skeletal).
When eating food, is it likely to stimulate the release of insulin or glucagon and why?
Insulin
After a meal blood glucose levels rise as the nutrients from the meal are absorbed, to reduce the
levels insulin is released
During fasting which is the dominanthormone?
Glucagon
Pancreatic hormones are peptide/protein based, what is their mode of action on their target
cells?
Water soluble therefore use the indirect (second messenger) mechanism of action on the target
cells
indirect mechanism proces
1 The water-soluble hormone travels in the blood as a free hormone.
2 The water-soluble hormone diffuses out of the capillary into the interstitial fluid.
3 The hormone attaches to a receptor on the surface ofthe target cell plasma membrane.
4 The receptor/hormone complex activates G-proteins located just beneath the surface of the cell membrane.
5 G-proteins alter the activity of an enzyme called Adenyl-cyclase.
6 ATP is enzymically converted to cyclic AMP (cAMP), which acts as a second messenger
(the hormone being the first messenger).
7 Protein-kinases (regulatory enzymes) are activated by cAMP.
8 Various cell processes are altered by protein kinases.
direct mechanism process
1 The lipid soluble hormone travels in the blood attached to a binding protein.
2 Lipid soluble hormone is released from its binding protein in the blood.
3 The lipid soluble hormone diffuses out of the capillary into the interstitial fluid.
4 Lipid soluble hormone diffuses through the plasma membrane of its target cell.
5 The lipid soluble hormone binds to a cytoplasmic receptor.
6 The receptor/hormone complex travels to the nucleus.
7 The receptor/hormone complex binds to the DNA.
8 This activates the production of mRNA molecules.
9 The mRNA moves to the cytoplasm to be translated into specific
peptide/polypeptides and proteins.
