Explanation

The heart consists of four chambers in which blood flows.

Blood enters the right atrium and passes through the right ventricle.

The right ventricle pumps the blood to the lungs where it becomes oxygenated.

Explanation

The Midbrain is the auditory relay centre and the centre that controls the reflex movements of the eyes. 

Explanation

The correct pathway of a nerve impulse is Receptors → CNS → Effectors. 

Receptors:

• These are specialized cells that detect stimuli (changes in the environment) like light, temperature, or pressure.
• They convert these stimuli into electrical signals.

CNS (Central Nervous System):

• This includes the brain and spinal cord.
• The sensory neurons transmit the electrical signals from the receptors to the CNS.
• In the CNS, the information is processed and a decision is made about how to respond.

Effectors:

• These are the organs or muscles that carry out the response.
• The CNS sends motor neurons to the effectors, which then trigger the muscle to contract or gland to secrete a substance. 

Explanation

A normal human has 23 linkage groups. 

A linkage group is defined as all the genes located on a single chromosome that tend to be inherited together.

The number of linkage groups in an organism is equal to its haploid number of chromosomes (n).

Humans have 46 total chromosomes, which are organized into 23 pairs (the diploid number, 2n).

The haploid number (n) in humans is 23, meaning there are 23 distinct types of chromosomes.

Therefore, there are 23 linkage groups in a normal human, corresponding to the 22 pairs of autosomes and one pair of sex chromosomes (XX in females or XY in males, considered as one linkage group in the general "normal human" context). 

Explanation

Central chemoreceptors that monitor the levels of CO₂ in the blood are primarily located in the medulla oblongata. 

Specifically, they are found on the ventrolateral surface of the medulla oblongata in areas such as the retrotrapezoid nucleus (RTN) and the medullary raphe.

These receptors are susceptible to changes in the hydrogen ion concentration (pH) of the cerebrospinal fluid (CSF), which is directly and rapidly influenced by arterial CO₂ levels, as CO₂ can easily cross the blood-brain barrier.