Homeostasis (F5)

1.      Must remember these 3 (very important) :

                                                        i.            Blood osmotic pressure (involves water)

                                                      ii.            Blood glucose level

                                                    iii.            Body temperature

2.      Regulation of blood osmotic pressure :

Situation A

                                i.            Drink too much water

                              ii.            Blood osmotic pressure …………………………….

                            iii.            Osmoreceptor in hy………………………. less stimulated

                            iv.            P…………………………… less stimulated

                              v.            Less …………….. is secreted into blood

                            vi.            Lower ……………….., d……………………………..& c……………………………are less permeable to water

                          vii.            Less water is re…………………………………

                        viii.            Urine contains more …………………. & means more d……………………..

                            ix.            Blood osmotic pressure increases back to normal

Situation B

                                i.            Drink too little water

                              ii.            Blood osmotic pressure …………………………..

                            iii.            Os………………………………. in h………………………….. detect and is s…………………..

                            iv.            Stimulate p………………………………….

                              v.            More ……………………….. is secreted into blood

                            vi.            Higher level of ……………………….. causes d…………………………….. & c………………………………. more permeable to water

                          vii.            M…………….. water is re…………………………

                        viii.            Urine contains less ……………………., more con………………………….

                            ix.            Blood osmotic pressure decreases back to normal

3.      Regulation of blood glucose level

Pancreas secretes hormones i……………………. and g………………………..

Situation A

                                i.            Blood glucose level increases (Eg. After meal), pancreas secretes hormone ………………………..

                              ii.            I…………………….. transported by bloodstream to liver, muscle cells, adipose tissue

                            iii.            I…………………….. stimulates liver to : use glucose for respiration, convert excess glucose to glycogen, stores excess glucose as glycogen

                            iv.            I…………………….. stimulates muscle cells to : use glucose for respiration, converts glucose to glycogen, store glycogen to build proteins

                              v.            I…………………….. stimulates adipose tissue to : use glucose for respiration, use glucose to form fat

Situation B

                                i.            Blood glucose level decreases (Eg. Fasting), pancreas secretes hormone ……………………

                              ii.            G…………………… transported by bloodstream to liver cells, adipose tissues

                            iii.            G…………………… stimulates liver to break down g…………………. into g……………….

                            iv.            G…………………… stimulates adipose tissue to break down l…………… which release fatty acids that can be metabolised to generate energy

4.      Regulation of body temperature

Normal body temperature 37⁰C (optimum temperature for metabolic reactions & enzyme activities)

Situation A

                                i.            Surrounding temperature is hot

                              ii.            Change in normal body temperature

                            iii.            T………………………………. in hypo…………………… detects blood temperature & t…………………………. in s……………… detects external temperature

                            iv.            Both t………………………………. send nerve impulses to hypothalamus

-          Action? V…………………………………… (arterioles dilate), smooth muscles around arterioles relax, more blood flows through skin, increase amount of heat radiated & loss via blood

-          Increase s…………………………., heat lost through surrounding when sweat evaporates, cools body down

-          Hair e………………………………… in the skin relax, warm air is not trapped & free to escape

-          Adrenal gland & thyroid gland are less stimulated to secrete a…………………………….. and t……………………………, thus metabolic rate is low & no excess heat generated

-          No shivering

-          Decrease body temperature

Situation B

                                i.            Surrounding temperature is cold.

                              ii.            Change in normal body temperature.

                            iii.            T…………………………………. in hypo…………………… detects blood temperature & t………………………….. in s………………….. detects external temperature

                            iv.            Both ………………………………….. send nerve impulses to hypothalamus

-          Action? V………………………………… ( arterioles constrict), smooth muscles around arterioles c…………………., d…………………… amount of blood flows through skin, d……………………. amount of heat loss

-          Sweating does not occur

-          Hair e……………………………………… in the skin c…………….., trapping & insulating air; preventing air from e……………………

-          A……………………………….. & T…………………………. are stimulated to secrete more a…………………………. & t………………, thus increases m………………………………. & generates more h…………….

-          Skeletal muscles are stimulated; s……………………. occurs; heat is generated

Our Brain

The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorise facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Afferent neurones gather information from the environment, send that info to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires off a response. Efferent neurones deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second.

The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla oblongata. Often the pons, and medulla oblongata are referred to together as the brainstem.

The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

What do each of these lobes do?

• Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
• Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli
• Occipital Lobe- associated with visual processing
• Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech

Note that the cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it. We will discuss the relevance of the degree of cortical folding (or gyrencephalisation) later.

A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. 

Sometimes the right hemisphere is associated with creativity and the left hemisphere is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres.

Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibres underneath carry signals between the nerve cells and other parts of the brain and body.

The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc).

The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance.

The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. 

Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old.

This system contains the thalamus, hypothalamus, amygdala, and hippocampus.

Thalamus- a large mass of gray matter deeply situated in the forebrain at the topmost portion of the diencephalon. The structure has sensory and motor functions. Almost all sensory information enters this structure where neurons send that information to the overlying cortex. Axons from every sensory system (except olfaction) synapse here as the last relay site before the information reaches the cerebral cortex.

Hypothalamus - part of the diencephalon, ventral to the thalamus. The structure is involved in functions including homeostasis, emotion, thirst, hunger, circadian rhythms, and control of the autonomic nervous system. In addition, it controls the pituitary. 

Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the "simplest" part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem. 

Midbrain/ Mesencephalon - the rostral part of the brain stem, which includes the tectum and tegmentum. It is involved in functions such as vision, hearing, eye movement, and body movement. The anterior part has the cerebral peduncle, which is a huge bundle of axons travelling from the cerebral cortex through the brain stem and these fibres (along with other structures) are important for voluntary motor function.

Pons- part of the metencephalon in the hindbrain. It is involved in motor control and sensory analysis... for example, information from the ear first enters the brain in the pons. It has parts that are important for the level of consciousness and for sleep. Some structures within the pons are linked to the cerebellum, thus are involved in movement and posture. 

Medulla Oblongata - this structure is the caudal-most part of the brain stem, between the pons and spinal cord. It is responsible for maintaining vital body functions, such as breathing and heart rate.

Kidney Failure

Kidney failure occurs when your kidneys are not working well. The kidneys cannot filter out toxins from your blood and will build up. The worse the kidney failure the more the toxins will build up

Kidney failure is detected by checking the blood for toxins normally cleared by the kidneys such as Urea and Creatinine. In kidney failure, the level of Urea and Creatinine in the blood will be raised. Ultrasound is usually done to check the size and texture of the kidneys as well as to look for stones or blockage to the kidneys. If both kidneys are shrunken, it usually means that the kidney failure has been present for sometime and the kidney damage is irreversible.

Ultrasound is not sensitive to detect early kidney failure. The kidneys will shrink only after the kidney damage has been present for a long time so a normal ultrasound does not always mean that the kidneys are normal.

If both kidneys failed, toxins build up in your blood.

Often people with mild kidney failure do not feel unwell. The condition is sometimes detected only during medical examination, urine or blood tests. In chronic kidney failure the kidney fails slowly and most patients do not feel ill until the kidneys have failed almost completely.

Symptoms of kidney failure are unfortunately vague and happen late. Often kidney failure does not cause any problems until the kidneys have almost completely failed. You may feel tired, less energetic, have poor appetite, nauseated and itchy. You also become more pale and your skin may darken and develop swelling in the feet or may be puffy in the face. Eventually you may start to vomit and become breathless. You can become pale and your skin may darken.

Most patients can still pass urine even when the kidney failure is very bad. It can take several years for dialysis patients to completely stop passing urine.

There are two types of kidney failure - acute kidney failure and chronic kidney failure. In acute kidney failure the kidney stops functioning suddenly. In many cases the kidney will recover if treated quickly. In chronic renal failure however there is long-standing kidney damage and scarring and it cannot be reversed even with medication.

Discuss with your doctor about definitive treatment for your kidney disease. However many kidney diseases cannot be cured and treatment will not cure any damage already present in the kidneys.