5.4. Integration of body systems Flashcards
Differentiate between tissue, organ and body system
Which organ systems coordinate all others?
Tissue contains single or multiple cell types and cells communicate by chemical and electric signals. Organs contain multiple tissue types. Body systems (eleven) contain physically linked organs (respiratory, digestive) or organs dispersed around the body (nervous, endocrine).
Nervous and endocrine systems integrate and coordinate all body systems.
Organization of the human nervous system
- Central (CNS); brain and spinal cord – relay neurons/interneurons
- Peripheral (PNS); somatic (voluntary) and autonomic (involuntary) – sensory and motor neurons
What is a nerve?
What different types of nerves are there?
What nerve is the largest in the body?
a bundle of neurons enclosed in a protective coating. Some nerves only contain sensory (optical nerve), some only motor, and some both types of neurons.
Sciatic nerve is the largest nerve in the body.
What does a sensory/motor/relay neuron do?
Sensory neuron – receives information from receptors about internal or external environment of the body (eyesight and touch in somatic and internal movements, pH, concentration, temperature in autonomic) and transmits it to the CNS. Cell body is positioned in the middle of the cell (on the axon).
Motor neuron – receives information from the CNS and transmits it to the effector (skeletal muscles in somatic and smooth muscles and glands in autonomic NS) – e.g. brain sends an impulse to the adrenaline gland (directly because endocrine system is slow). Cell body is located on the terminal (one side of the neuron).
Interneurons (relay) carry impulses within the CNS from one to another neuron – connecting motor and sensory
How is the brain divided? What is the function of each structure?
1) Cerebrum (big brain) is made of
a) cerebral cortex (surface of the cerebrum made of grey matter (dendrites)) and
b) white matter (inside of cerebrum made of axon terminals). Cortex receives impulse and processes it.
2) Hind brain is made of
a) cerebellum (small brain) which coordinates and fine tunes the contraction of skeletal muscles, regulates balance, timing and coordination of muscles and muscle memory and
b) medulla oblongata that has autonomic functions like cardiovascular centre, pH and temperature control, etc.
3) Most of the 12 pairs of cranial nerves are connected to the hind brain.
4) Hypothalamus and pituitary gland are a part of the nervous system but have control over the entire endocrine system.
Brain functions:
- Receives information
- Processes information (decision making)
- Stores information (memory, more synapses = better memory)
Where is the spinal cord located? What is its function? How are nerves positioned in it?
Spinal cord is inside the vertebral column, closer to the dorsal side (ventral (front) and dorsal (back)) it has white matter on the surface and grey matter on the inside. It is the integration centre for unconscious processes, and it can make decisions by itself regarding info brought by sensing neurons (e.g. reflexes) or send the impulse to the brain. 31 pairs of spinal nerves are connected to it. Sensory nerve roots are on the dorsal side and motor nerve roots on the ventral side.
How does a stimulus cause a reaction (describe the pathway of signal)?
Stimulus, as a type of energy from internal or external environment (touch, sound, stretch, chemicals, light…), is converted into electrical energy by receptors, the nerve impulse is conducted by sensory nerves to the relay nerves in CNS where information is processed, and the impulse is then carried by motor neurons to the effectors (muscle or gland) that carry out the response to the stimulus.
What is a reflex arc? Describe one example of it (describe the pathway of signal).
Synapses between neurons in reflex arc are located in the spinal cord Example is pain reflex or photo-pupillary reflex.
Pupillary reflex – protecting the retina from overly bright light – bright light is detected by photoreceptors (cons and rods) in the retina, signal travels to the optical centre in the brain via cranial nerves, signal is sent by motor neurons to the smooth muscles in the iris to contract and thus shrink the pupil.
what are the two forms receptors come in?
specialized receptors (stretch, chemoreceptors, photoreceptors in retina) or nerve endings (elongated dendrites) of sensory neurons (touch, heat)
What is feedback mechanism? What are potential variables of internal environment (and some corresponding receptors)?
Mechanism that controls internal environment of the body by detecting the change and responding to it by either counteracting the further change in the same direction (negative) or stimulating it (positive).
Variables of internal environment: temp of blood, p(CO2), p(O2), C(glucose) (only in pancreas), blood pressure (baroreceptors), C(blood) – chemoreceptors, thermal receptors, baroreceptors, stretch receptors, osmoreceptors (C(blood))
what is negative feedback mechanism? provide examples. How does it work (describe the process)?
When the nervous system undertakes action to counteract the perceived stimulus. For example, photo-pupillary reflex, heart rate and ventilation control and peristalsis.
Receptors detect changes of some variable in the body. This info is relayed to a coordinator that determines the level of response. The coordinator relays a decision to the effector that produces the response. The response will modify the internal environment, and new conditions will become new stimuli. The cycle continues until conditions are within acceptable limits.
Describe 1) ventilation control and 2) heart rate control by negative feedback mechanism.
1) Ventilation control: blood pH is too acidic, chemoreceptors in the vessel walls (aorta, carotid…) sense this, send an impulse via sensory neurons to the coordinator (a centre in medulla oblongata), impulse is sent back via motor neurons to muscles (diaphragm and intercoastal), ventilation is increased, less CO2 in the blood so blood pH increases to the homeostatic level (7.35-7.45 range).
2) Heart rate control: Blood pH and pressure (baroreceptors in carotid and aorta) info sent to the cardiovascular centre in medulla oblongata => if pH is too low sympathetic nerve stimulates the adrenal gland (effector) to release adrenaline into blood into myocardial cells to increase the heart rate and thus the turnover of blood => if pH is too high parasympathetic nerve stimulates lower heart rate (also called vagabond nerve or nervus vagus)
How does the intestine direct flow of materials through it? Which parts of digestive system are voluntary, and which are involuntary? What is the name of the NS that controls digestive system?
Intestine (ascending, transverse, descending) – longitudinal and circular muscles change the diameter and length of the intestine by intermittent contractions and relaxations and thus direct the flow of materials through the intestine
Enteric nervous system (controls digestive system) is the largest and most complex part of PNS. It is partly autonomic and partly somatic:
- Involuntary (peristalsis, smooth muscles of the oesophagus contract to push food down)
- Voluntary (striated muscle of tongue (pushing food to the back of the mouth), touch receptors in the pharynx (nerve impulse to the brain stem) and defecation/egestion (removal of faeces from rectum))
What does it depend on whether egestion is voluntary or involuntary and how? What type of a muscle is anus? What are enlarged vessels in that area called?
depending on the age (babies and older people involuntary, still hasn’t developed in babies, in older people gradual loss of nervous control leads to involuntary anal control)
Anus is a circular muscle – external is striated, internal smooth, rich blood supply needed
haemorrhoids
