I think the answer is "yes," that a yeerk's nervousness would make the host's heart speed up, mostly based on things Jake describes Tom's body doing at various points in the series:

He was making no effort to pretend to actually be Tom... His fists were clenched at his side, his jaw seemed to tighten so that the words could barely force their way past bared teeth. I'd seen Tom this way once, just once, when he'd been wrongly accused of cheating on a test. — #53

"What?" Tom's eyes bulged in shock. "Tuesday? Dad, no way! Four days? I can't stay away for four days!" "You can and you will," my father said, losing his patience. "We're going as a family and that's final." Tom's throat worked. — #31

I heard a sound that was strange because it was so normal. It was laughter. Human laughter. The humans... the Human-Controllers — because that's what they were — were laughing, like they were at some kind of a show [Elfangor's death]. For a moment it seemed to me that one of those laughing voices was familiar... —#1

[Temrash 114 implies that if Jake joins the Sharing, then he'll get out of having to do homework. Jake points out that that makes no sense.] Tom considered for a moment. He blinked and kind of looked away, almost like he was embarrassed. "No. I don't want you thinking that," he admitted. "Tell you what, though, come to the meeting and I'll help you do the homework when we get home." — MM4

This is one of my favorite tricks, picked up from E.M. Forester and filtered through my own domestic-homebody lens.  Forester says that you should never ever tell us how a character feels; instead, show us what those emotions are doing to a character’s posture and tone and expression.  This makes “I felt sadness” into “my shoulders hunched and I sighed heavily, staring at the ground as my eyes filled with tears.”  Those emotions-as-motions are called objective correlatives.  Honestly, fic writers have gotten the memo on objective correlatives, but sometimes struggle with how to use them.

Objective correlatives can quickly become a) repetitive or b) melodramatic.  On the repetitive end, long scenes of dialogue can quickly turn into “he sighed” and “she nodded” so many times that he starts to feel like a window fan and she like a bobblehead.  On the melodramatic end, a debate about where to eat dinner can start to feel like an episode of Jerry Springer because “he shrieked” while “she clenched her fists” and they both “ground their teeth.”  If you leave the objective correlatives out entirely, then you have what’s known as “floating” dialogue — we get the words themselves but no idea how they’re being said, and feel completely disconnected from the scene.  If you try to get meaning across by telling us the characters’ thoughts instead, this quickly drifts into purple prose.

Instead, have them wash the dishes while they talk.

To be clear: it doesn’t have to be dishes.  They could be folding laundry or sweeping the floor or cooking a meal or making a bed or changing a lightbulb.  The point is to engage your characters in some meaningless, everyday household task that does not directly relate to the subject of the conversation.

This trick gives you a whole wealth of objective correlatives.  If your character is angry, then the way they scrub a bowl will be very different from how they’ll be scrubbing while happy.  If your character is taking a moment to think, then they might splash suds around for a few seconds.  A character who is not that invested in the conversation will be looking at the sink not paying much attention.  A character moderately invested will be looking at the speaker while continuing to scrub a pot.  If the character is suddenly very invested in the conversation, you can convey this by having them set the pot down entirely and give their full attention to the speaker.

A demonstration:

1

“I’m leaving,” Anastasia said.

“What?”  Drizella continued dropping forks into the dishwasher.

2

“I’m leaving,” Anastasia said.

Drizella paused midway through slotting a fork into the dishwasher.  “What?”

3

“I’m leaving,” Anastasia said.

Drizella laughed, not looking up from where she was arranging forks in the dishwasher.  “What?”

4

“I’m leaving,” Anastasia said.

The forks slipped out of Drizella’s hand and clattered onto the floor of the dishwasher.  “What?”

5

“I’m leaving,” Anastasia said.

“What?”  Drizella shoved several forks into the dishwasher with unnecessary force, not seeming to notice when several bounced back out of the silverware rack.

See how cheaply and easily we can get across Drizella’s five different emotions about Anastasia leaving, all by telling the reader how she’s doing the dishes?  And all the while no heads were nodded, no teeth were clenched.

The reason I recommend having it be one of these boring domestic chores instead of, say, scaling a building or picking a lock, is that chores add a sense of realism and are low-stakes enough not to be distracting.  If you add a concurrent task that’s high-stakes, then potentially your readers are going to be so focused on the question of whether your characters will pick the lock in time that they don’t catch the dialogue.  But no one’s going to be on the edge of their seat wondering whether Drizella’s going to have enough clean forks for tomorrow.

And chores are a cheap-n-easy way to add a lot of realism to your story.  So much of the appeal of contemporary superhero stories comes from Spider-Man having to wash his costume in a Queens laundromat or Green Arrow cheating at darts, because those details are fun and interesting and make a story feel “real.”  Actually ask the question of what dishes or clothing or furniture your character owns and how often that stuff gets washed.  That’s how you avoid reality-breaking continuity errors like stating in Chapter 3 that all of your character’s worldly possessions fit in a single backpack and in Chapter 7 having your character find a pair of pants he forgot he owns.  You don’t have to tell the reader what dishes your character owns (please don’t; it’s already bad enough when Tolkien does it) but you should ideally know for yourself.

<< The pages of 20th century American literature are stuffed with stuff. When you begin to read for things, you will encounter them constantly: baseballs, bric-a-brac, books within books. There are dolls, chairs, paperweights, cans of ground coffee, red wheelbarrows. The plethora of objects on the page has fueled a branch of academic inquiry dubbed “thing theory”—a capacious subfield that ties together strands of material culture studies, art history, and literary studies, among other arenas. In his foundational book, A Sense of Things: The Object Matter of American Literature (2003), Bill Brown proposes a rereading of texts from the late 19th and early 20th centuries to “ask why and how we use objects to make meaning, to make or re-make ourselves, to organize our anxieties and affections, to sublimate our fears and shape our fantasies.” Brown reads for the relationship between things and ideas, and puts forth an account of literary objects that extends beyond commodity fetishism, a reading that stretches toward the strange vibrations of matter in literature and our lives.