Lecture 17, 28 Oct 2003 Chapter 12, Circulation (con t) Vertebrate Physiology ECOL 437 University of Arizona Fall 2003

Transcription

1 1 Lecture 17, 28 Oct 2003 Chapter 12, Circulation (con t) Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch

2 Vertebrate Physiology Circulation (CH12) 2. Announcements exams Wed Seminar Assgt. 3. Slide #s Sherwood 1997

3 2003 Vertebrate Physiology EXAM 2, 21 October # of students mean max min s.d n=20 Score out of 100

4 ANATOMY: The integument has a unique circulatory pattern that involves a shunting system through the reticular layer into the subcutaneous layer. This cutaneous plexus gives off tributaries to supply the adipose tissue of the subcutaneous layer and the tissues of the integument. As the cutaneous plexus approaches the papillary layer they terminate in the capillaries of the dermal papillae. These branches supply the hair follicles, sweat glands, and other structures in the dermis. The unusual thing about these capillaries is that the small arteries and arterioles that supply them are organized into another interconnecting system call the papillary plexus. The papillary plexus provides arterial blood to the capillary loops that follow the contours of the dermal papilla at the epidermal-dermal boundary to feed the structures mentioned above. The venous network returns the blood back to the body core by following the arterial pattern exactly. Once you have the anatomy under control they the physiology follows from the structure of the blood flow pattern. Cold, red skin? PHYSIOLOGY: When the skin is challenged by cold, the first thing that happens is the smooth muscle surrounding the small arteries and arterioles going from the cutaneous plexus through the reticular layer to the papillary plexus constrict to conserve body heat. This action shunts the blood away from the reticular and papillary layers and keeps it in the deeper subcutaneous layers. Just the opposite happens when a person gets over-heated, along with sweating, to reduce body heat. In that case the warm blood from the deeper layer is shunted into, rather than away from, the papillary layer so that the cooling effect of evaporating sweat will be maximized as the warm blood passes through the cooler dermal capillary loops before going into the venous tree. Something fascinating happens in the cold response, however. Since tissue will die without having oxygen and nutrients delivered and waste products removed over time, the shunting mechanism cannot shut down indefinitely. Depending on how cold the area of skin gets, the smooth muscle will reduce its contraction every so often. This will occur at 5 to 15 minute intervals, as I said depending on the degree of cold on that particular skin surface. Some people have inappropriate spasms of the smooth muscle that greatly restrict the flow to the dermis and then, after a severe cold period that can become painful, the vessels will dilate much more than normal and cause the skin to be a bright pink or red. This phenomenon is most common in the digits of hands and feet and is most frequently found in young women. The case is unknown (idiopathic). The person can actually have a triphasic color change starting with pallor (shutting down of the blood flow), moving to cyanosis (bluish color due to reduction of oxygen and build up of carbon dioxide), and then reactive hyperemia (redness). This problem was described by a doctor named Raynaud and is now referred to as Raynaud s disease. 3b

5 Name that student: 4 Lauren Mashaud Cricket research Linda Webb Psychology Sarju_Govani Dines at DD

6 5 Recall AP and refractory period differences (12-7)

7 Types of Cardiac Cells: 6 A. Contractile B. Conducting ~ autorhythmic SA node AV node ~ fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Vander 2001 (see 12-5)

8 Sherwood

9 Types of Cardiac Cells: 8 A. Contractile B. Conducting - 1 autorhythmic SA node AV node -1 fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Pacemakers: -Normally HR driven by SA node -Others are Latent pacemakers -Called Ectopic pacemaker when node other than SA driving HR

10 Sherwood ~ SA node ~ latent rate Sherwood 1997

11 Sherwood 1997 SA AV other oops 10 The Heart Rate Train

12 9-11, Sherwood Which way would you alter channel permeabilities to speed or slow HR?? ~Transient Ca 2+ channels K +, Na + Autorhythmic Cardiac Muscle (e.g. SA node)

13 12 Sherwood 1997 Contractile Cardiac Muscle Ca 2+ current maintains plateau Vander 2001

14 13 (12-8) (Q,R,S masks atrial repolarization)

15 (12-8) 14

16 Wiggers Diagram Valves open/close where pressure curves cross 760 mmhg = 1 atm = 9.8 m blood 15 1: , Vander 2001 (See 12-12)

17 16 Sherwood 1997 Atrial Kick Heart filled ~same with increased HR

18 Sherwood Frank-Starling Curve (p. 483) Systole = Ventricular Emptying Diastole = Ventricular Filling (rest) Vander 2001

19 18 Heart Work Loops (12-13)

20 Cardiac Output: 18b CO = cardiac output (ml/min from 1 ventricle) SV = stroke volume (ml/beat from 1 ventricle) = EDV ESV (end-diastolic end-systolic volume) HR = heart rate (beats/min) CO = HR x SV MABP = CO x TPR MABP = DP + 1/3(SP-DP) - Heart can utilize different types of energy sources (unlike brain)

21 HR control Parasympathetic vs. Sympathetic 19 (12-5)

22 (12-6) 20

23 Cardiac Output Control 21 Sympathetic speeds heart rate and increases contractility 1. Norepinephrine binds to beta 1 adrenergic receptors 2. Increases camp levels and phosphorylation 3. Activates cation channels (Na + ) and increases HR 4. Epi and Norepi activate alpha and beta 1 adrenoreceptors which increase contractility and rate of signal conduction across heart

24 22 How increase contractility? More Ca 2+ Vander 2001

25 HR control 23 Parasympathetic slows heart rate -Innervate Atria (Vagus nerve = Xth cranial nerve) -Cholinergic (ACh) -Alter SA node pacemaker potential by K + permeability Ca 2+ permeability Parasympathetic innervation of AV node slows passage of signal between atria and ventricles

26 Hemodynamics in Vessels Flow depends primarily on pressure gradient and resistance , Vander 2001 Vander 2001

27 Hemodynamics - Poiseuille s Law: Use to approximate flow 25 Pressure Gradient Flow rate radius 4 Q = (P 1 P 2 )πr 4 8Lη length viscosity Small change in radius large change in flow rate

28 Hemodynamics - From Poiseuille s Law: 26 Resistance Pressure Gradient length viscosity R = (P 1 P 2 ) Q = 8Lη πr 4 Flow rate radius 4 Small change in radius large change resistance Modifiable if vessel distensible under pressure

29 End xx