Serum Lipids

• Total cholesterol is the sum of
  • HDL cholesterol
  • LDL cholesterol and
  • 20% of the triglyceride value
• Note that
  • high LDL values are bad, but
  • high HDL values are good.
• Using the various values, one can calculate a
  cardiac risk ratio = total cholesterol divided by HDL cholesterol
• A cardiac risk ratio greater than 7 is considered a warning.

Functions of the nervous system:

1) Integration of body processes

2) Control of voluntary effectors (skeletal muscles), and mediation of voluntary reflexes.

3) Control of involuntary effectors (  smooth muscle, cardiac muscle, glands) and mediation of autonomic reflexes (heart rate, blood pressure, glandular secretion, etc.)

4) Response to stimuli

5) Responsible for conscious thought and perception, emotions, personality, the mind.

AdenosineTriphosphate (ATP)

• Animal cells cannot directly use most forms of energy
  • Most cellular processes require energy stored in the bonds of a molecule, adenosine triphosphate (ATP)
  • ATP is referred to as the energy currency of the cell

It is a nucleotide, formed from:

• the base adenine (the structure with 2 rings),
• the 5 carbon sugar deoxyribose (one ring)
• 3 phosphates

Energy is stored in the bonds between the phosphates and is released when the bonds are broken

Characteristics of Facilitated Diffusion & Active Transport - both require the use of carriers that are specific to particular substances (that is, each type of carrier can 'carry' one type of substance) and both can exhibit saturation (movement across a membrane is limited by number of carriers & the speed with which they move materials

• The Autonomic Nervous System (ANS) Controls the Body's Internal Environment in a Coordinated Manner

• The ANS helps control the heart rate, blood pressure, digestion, respiration, blood pH and other bodily functions through a series of complex reflex actions
• These controls are done automatically, below the conscious level
• To exert this control the activities of many different organs must be coordinated so they work to accomplish the same goal
• In the ANS there are 2 nerves between the central nervous system (CNS) and the organ. The nerve cell bodies for the second nerve are organized into ganglia:
  • CNS -> Preganglionic nerve -> Ganglion -> Postganglionic nerve -> Organ
• At each junction neurotransmitters are released and carry the signal to the next nerve or organ.

• The ANS has 2 Divisions, Sympathetic and Parasympathetic

   

• Comparison of the 2 systems:

• 	Anatomical Location	Preganglionic Fibers	Postganglionic Fibers	Transmitter (Ganglia)	Transmitter (Organs)
  Sympathetic	Thoracic/ Lumbar	Short	Long	ACh	NE
  Parasympathetic	Cranial/ Sacral	Long	Short	ACh	ACh

   

  The Sympathetic is the "Fight or Flight" Branch of the ANS

• Emergency situations, where the body needs a sudden burst of energy, are handled by the sympathetic system
• The sympathetic system increases cardiac output and pulmonary ventilation, routes blood to the muscles, raises blood glucose and slows down digestion, kidney filtration and other functions not needed during emergencies
• Whole sympathetic system tends to "go off" together
• In a controlled environment the sympathetic system is not required for life, but it is essential for any stressful situation

• The Parasympathetic is the Rest and Digest Branch of the ANS

• The parasympathetic system promotes normal maintenance of the body- acquiring building blocks and energy from food and getting rid of the wastes
• It promotes secretions and mobility of different parts of the digestive tract.
• Also involved in urination, defecation.
• Does not "go off" together; activities initiated when appropriate
• The vagus nerve (cranial number 10) is the chief parasympathetic nerve
• Other cranial parasympathetic nerves are: III (oculomotor), VII (facial) and IX (glossopharyngeal)

• The Hypothalamus Has Central Control of the ANS

• The hypothalamus is involved in the coordination of ANS responses,
• One section of the hypothalamus seems to control many of the "fight or flight" responses; another section favors "rest and digest" activities

• The Adrenal Medulla is an Extension of the Sympathetic Nervous System

• The adrenal medulla behaves like a combined autonomic ganglion and postsynaptic sympathetic nerve (see diagram above)
• Releases both norepinephrine and epinephrine in emergency situations
  • Releases a mixture of epinephrine (E = 80%) and norepinephrine (NE = 20%)
  • Epinephrine = adrenaline
• This action is under control of the hypothalamus

• Sympathetic & Parasympathetic Systems

• Usually (but not always) both sympathetic and parasympathetic nerves go to an organ and have opposite effects
• You can predict about 90% of the sympathetic and parasympathetic responses using the 2 phrases: "Fight or Flight" and "Rest and Digest".
• Special cases:
  • Occasionally the 2 systems work together: in sexual intercourse the parasympathetic promotes erection and the sympathetic produces ejaculation
  • Eye: the sympathetic response is dilation and relaxation of the ciliary muscle for far vision (parasympathetic does the opposite)
  • Urination: the parasympathetic system relaxes the sphincter muscle and promotes contraction of muscles of the bladder wall -> urination (sympathetic blocks urination)
  • Defecation: the parasympathetic system causes relaxation of the anal sphincter and stimulates colon and rectum to contract -> defecation (sympathetic blocks defecation)

• Organ	Parasympathetic Response "Rest and Digest"	Sympathetic Response "Fight or Flight"
  Heart (baroreceptor reflex)	Decreased heart rate Cardiac output decreases	Increased rate and strength of contraction Cardiac output increases
  Lung Bronchioles	Constriction	Dilation
  Liver Glycogen	No effect	Glycogen breakdown Blood glucose increases
  Fat Tissue	No effect	Breakdown of fat Blood fatty acids increase
  Basal Metabolism	No effect	Increases ~ 2X
  Stomach	Increased secretion of HCl & digestive enzymes Increased motility	Decreased secretion Decreased motility
  Intestine	Increased secretion of HCl & digestive enzymes Increased motility	Decreased secretion Decreased motility
  Urinary bladder	Relaxes sphincter Detrusor muscle contracts Urination promoted	Constricts sphincter Relaxes detrusor Urination inhibited
  Rectum	Relaxes sphincter Contracts wall muscles Defecation promoted	Constricts sphincter Relaxes wall muscles Defecation inhibited
  Eye	Iris constricts Adjusts for near vision	Iris dilates Adjusts for far vision
  Male Sex Organs	Promotes erection	Promotes ejaculation

   

Typical Concentration Gradients and Membrane Potentials in Excitable Cells

The Na Pump is Particularly Important in the Kidney and Brain

• All cells have Na pumps in their membranes, but some cells have more than others
• Over-all Na pump activity may account for a third of your resting energy expenditure!
• In the kidney the Na pump activity is very high because it is used to regulate body salt and water concentrations
  • Kidneys use enormous amounts of energy: 0.5% of body weight, but use 7% of the oxygen supply
• Pump activity is also high in the brain because Na and K gradients are essential for nerves
  • The brain is another high energy organ; it is 2% of body weight, but uses 18% of the oxygen supply

In the Resting State Potassium Controls the Membrane Potential of Most Cells

• Resting cells have more open K channels than other types
• More K+ passes through membrane than other ions- therefore K+ controls the potential
• Blood K+ must be closely controlled because small changes will produce large changes in the membrane potentials of cells
  • Raising K will make the membrane potential less negative (depolarization)
• High blood K+ can cause the heart to stop beating (it goes into permanent contraction)

During an Action Potential Na Channels Open, and Na Controls the Membrane Potential

• Whichever ion has the most open channels controls the membrane potential
• Excitable cells have Na channels that open when stimulated
• When large numbers of these channels open Na controls the membrane potential