Control Systems and Biological Rhythms

Endocrine System

Endocrine glands are specialized groups of cells tat secrete their products (hormone) directly into the bloodstream

The _______ and _______ _______ are the master control mechanisms of the endocrine system

Hypothalamus and pituitary gland

Hypothalamus

- Forebrain

- Control pituitary gland

- Uses neural and hormonal pathways

- Neural pathways posterior pituitary

- Hormonal pathways anterior pituitary

Pituitary Gland composed of two structurally and functionally distinct lobes:

Adenohypophysis (anterior lobe) and Neurohypophysis (posterior lobe)

Adenohypophysis

Secretes various hormones (prolactin, TSH, ACTH, FSH, LH, etc) that regulate many processes: growth, lactation, ovulation, metabolic rate, heart and digestive functions

Neurohypophysis

- ADH maintain blood pressure, volume, eater balance, urine concentration, etc

- Oxytocin stimulates contraction of the uterus during birth, important in lactation, sperm production, etc.

Thyroid gland

Located in neck just below the larynx

Parathyroid gland

- Four small glands on posterior surface of thyroid gland

- Calcium regulation on blood and bones

Pancreas

- Both exocrine and endocrine functions

- Islets of Langerhan represent the endocrine portion of the pancreas (1-2% in humans)

- Within the islets of Langerhans are: Alpha cells and

Beta cells

Alpha cells

produce glucagon

Beta cells

produce insulin

Adrenal Glands

- Paired glands on top of kidneys, adrenal cortex

- Adrenal medulla

- Produces: Epinephrine, Norepinephrine, Fight or flight response

Biological Rhythms

patterns of activity that occur at regular intervals during the life of the animal

3 Main Types of Rhythms

Circadian, Circannual, and Ultranian

Circadian Rhythms

Period of 24 Hours

- Diurnal, Nocturnal, and Crepuscular

- Photoperiod: primary cue (Zeitgeber), time keeper

Circannual Rhythms

Period of 1 year

- Regulates: Seasonal changes in pelage color, Hibernations, and Reproduction

- Photoperiod - primary cue (usually)

Ultradian Rhythms

period of less than 24 hours

- Repetitive cycles throughout the day

- Photoperiod probably also plays a role on the timing of these activities, not as understood/clear

Photoperiod

the period of daily illumination received by an organism